Scratch arduino tutorial jobs
...website that you might find useful to copy as well as UI elements that might make this project make more sense. Another option that you can replicate: Things you need to know: I expect you to test this tool yourself and provide proof of function before receiving any payment. You will need to download the game and client, create an account, and develop a tutorial on how to install and use the tool. I will pay for any additional quality of life changes made to the tool that I ask for after a working software is made. We will use discord to communicate, please make sure you PM me with your discord name so we can discuss the project and cost. I will be paying a combined upfront cost for the development and then subsequent costs for updates done to the tool
...responses on Messenger. Many people respond to our ad with a like or a love, but they do not leave a comment. Key Requirements: 1. Send personalized messages through Messenger to these individuals without sending friend requests. 2. Ensure that my responses show up in the inbox of Meta Business Suite. 3. Deliver the messages in a way that allows these individuals to respond. 4. Provide a simple tutorial on how to do this myself in the future. 5. Track recipients' responses. 6. Segment recipients based on their reactions. Ideal Skills and Experience: - Proficiency with Meta Business Suite and Messenger - Experience in social media management - Ability to create personalized messages - Data tracking and analysis skills - Experience in creating simple tutorials for non-tech ...
I'm looking for an SEO professional who can help push my website to the first page of Google search. The primary keywords I'm targeting are "tiktok shop wms" and "tiktok shop warehouse management system". Key Responsibilities: - Develop a comprehensive SEO strategy from scratch as I currently do not have one in place. - Focus on overall site ranking improvement, not just specific keywords. - Enhance brand visibility and increase organic traffic. Ideal Skills and Experience: - Proven track record of improving search engine rankings. - Extensive knowledge of SEO tools and techniques. - Strong understanding of Google’s ranking algorithms. - Experience in e-commerce and warehouse management system SEO is a plus. website is
I'm looking for a professional educator with experience in the broker industry to create engaging video tutorials for beginners about EO Broker. Key Requirements: - Expertise in the EO Broker platform - Proven experience in educational content delivery, particularly via video - Ability to break down complex concepts into simple, understandable lessons for beginners Your role will be to design and deliver a series of video tutorials that are clear, engaging and accessible for beginners. You should be skilled in both the content and delivery, able to convey complex broker concepts in a simple, digestible way. Experience in video production and editing would be a plus.
I own a company that sells flooring in Italy, and I would like to implement advertising on social media for a catalog of 30 products. I would like to advertise on: Facebook (Shopify integration available) YouTube (Shopify integ...Pinterest (Shopify integration available) Twitter (Shopify integration available through third-party apps) Snapchat (Shopify integration available through third-party apps) Telegram (Shopify integration not directly available; bots or external tools can be used) I need a detailed proposal for all or only part of the described social platforms. All accounts would be newly created and built from scratch with images and content provided by me. Additionally, where possible, the 30 products would need to be uploaded and linked to a website to be developed wit...
I'm looking for an Angular expert to help me develop a Progressive Web Application (PWA) from scratch on a per-hour basis. The ideal candidate should have extensive experience with Angular and PWA development, and be capable of implementing the core features of this project, which include: - Offline capabilities: The application should be able to function without internet connectivity, caching resources and enabling users to access content offline. - Push notifications: I want to incorporate real-time updates and alerts to engage users and enhance their experience. - Responsive design: The application should provide a seamless experience across all devices, from desktops to smartphones. If you have a strong portfolio of Angular and PWA projects, and can deliver high-quality, ...
...Export translations in a structured format (e.g., DOCX or TXT). Provide side-by-side output showing the original text and its translation. Process Automation: Automate processing for multiple pages or files. Allow users to add new comics, and the program will extract, translate, and save the output automatically. Requirements: The program must use external AI services (not create an AI from scratch). It should support integration with popular AI tools via APIs. Ensure accurate text extraction, even with stylized fonts. Ideal Skills and Experience: Experience with OCR (Optical Character Recognition) technologies. Proficiency in programming languages such as Python, Java, or C#. Strong understanding of API integrations with AI tools like Google Translate, DeepL, or OpenAI. Famil...
Job Ad: Professional Web Developer Needed for Hotel Advertisement Platform We are looking for an experienced and professional web developer who can complete the project by strictly deadline end of January [3 weeks] Can code in React (Frontend) frpm scratch as on but with some modern technologies which elements you can see in attach scope of work and Node.js (Backend) which we already have. Developer must have previous experience with hotel-related platforms and can provide proof of previous work. Understands the intricacies of developing large-scale platforms similar to Booking.com. Project Overview: We are developing an advertisement platform for hotels, not a booking platform. This platform will: 1. Allow hotels to list themselves using advanced AI technology
Hi there! I’m looking for a creative freelancer who can help me recreate a specific scene by drawing it from scratch or generating it using AI. This is not a simple photo editing task—I want the final result to be original and unique. Here’s the task: • The original photo has three individuals: 1. A police officer in the foreground (leave as is). 2. A man with his hand raised (we’ll call him “Vitalik”). This person needs to be removed from the scene. 3. A person standing in the doorway in the background. This individual should be moved to where “Vitalik” is currently standing. To make it easier, I’m providing a second photo (in private message) of the person in the doorway as a reference for their features. The style...
...direction, and anchoring. As part of this project, I expect the developer to: - Propose suitable technologies and frameworks for a lightweight and efficient solution. - Deliver a PoC demonstrating polished functionality and visual appeal. - Provide source code, all created assets, and comprehensive documentation. The game's visual style is minimalistic, and all game assets need to be created from scratch. The preferred engine for this project is Unity. Ideal candidates should have: - Extensive experience in mobile game development, particularly with Unity. - A strong understanding of creating engaging and intuitive gameplay. - Skills in minimalist game design and asset creation. - Ability to deliver a visually appealing and functional PoC. Please refer to the attached t...
More details: What primary functionality should the WPA app provide? Task management Which platforms do you want the WPA app to support? Web, iOS, Android What key features do you want in the task management WPA app? Task assignments, Deadline tracking, Notifications
I'm seeking a talented bicycle designer specializing in hybrid bikes. Your main focus will be on designing the frame, selecting the wheel and tire specifications, and creating the gear and brake systems. Key Responsibilities: - Designing a frame for a hybrid bike from scratch - Specifying appropriate wheels and tires - Developing an efficient gear and brake system Ideal Skills: - Proven experience in bicycle design, particularly with hybrid bikes - Proficiency in CAD software or similar design tools - Strong understanding of bicycle mechanics and engineering principles
I have an existing working TensorFlow code that requires modifications to enhance training performance and improve model test metric. I do not need a new code from scratch, but rather an expert who can make targeted changes to my existing code and run it on a gpu. I need a fully trained model within 2-3 days. My model has about half a million parameters and any changes to Network architecture must ensure the parameter count stays within one million. My test metric is miou and I want to achieve 80% while my current model gives me roughly 40%. Besides that, the final model should run on a CPU. Gpu is only required to make training faster. Key Requirements: - Access to a GPU and expertise in utilizing it for deep learning tasks - Proven experience with training deep learning networks ...
I must do a web application in wordpress. It must have a landing page stile, the payment of service, so creation of account, login and payment. It must have a form plugin to do questionnaire. At th eend of the questionnaire the AI must show a report baed on answers. The web must have a form plugin jotform) The job to do: make the landing pages with information of service, add the buy pa...already create using the Ai the plugin to create the datbse but it is necessray make some changes. Other important think is create a pligin or code to create the comunication between the plugin uncanny or Ai engine. I have already installed inside the domin wordpress, jotform, uncanny, elementor, the plugin to creat ethe datbse. So you can decide to use my application to do all changes or make from sc...
Job Title: Android Developer Experience: 2+ Years Location: Remote or On-site Job Description: We are seeking a skilled Android Developer to join our team. The ideal candidate will be responsible for maintaining existing codebases and developing new features and applications from scratch. Responsibilities: Maintain, debug, and enhance existing Android applications. Design and develop new Android applications and features. Collaborate with cross-functional teams to define, design, and ship new functionalities. Ensure the best possible performance, quality, and responsiveness of applications. Stay updated with the latest trends and best practices in Android development. Requirements: Proven experience of 2+ years in Android development. Strong knowledge of Java or Kotlin. Familiarit...
I need a detailed, step-by-step tutorial on how to complete a specific document formatting project in Word. Ideal Skills and Experience: - Proficiency in Microsoft Word - Experience in creating instructional materials - Ability to simplify complex tasks into easy-to-follow steps - Prior experience in document formatting is a plus.
I need a desktop-based software for an ESP32 development module educational kit. This software should allow users to write code, compile and u...educational kit. This software should allow users to write code, compile and upload it to the module. It should support different sensors and provide a user-friendly Graphical User Interface (GUI). Key Requirements: - Code writing in Scratch, C and Python - Compilation and uploading to the ESP32 module - Interaction with various sensors - Intuitive GUI - Compatibility with Windows and MacOS Ideal Skills: - Proficient in software development for educational purposes - Experience with ESP32 and various sensors - Skilled in creating GUI software - Knowledgeable in Scratch, C and Python - Able to ensure cross-platform compatibility (W...
I'm working on a project for my BMW E60 and I need a professional with Arduino coding experience to help me with the programming. The project involves creating a remote start system that uses either the Nano 33BLE or an ESP with a CAN bus module. The system will also incorporate a fingerprint module and various other safety sensors. Key aspects of the project include: - All coding needs: This includes the coding for the remote start using the fingerprint module, the remote unlock functionality using BLE or standard Bluetooth, and the integration of the CAN bus and other safety sensors. - Focus on all elements: The coding assistance required will cover every aspect of the project, from the integration of the CAN bus module to the configuration of the BLE/standard Bluetooth for ...
I'm seeking a comprehensive tutorial focused on practical project walkthroughs of Model-Driven Power Apps. This tutorial should be designed for beginners but also cover a variety of advanced features. Key Aspects of the Tutorial: - Practical project walkthroughs that allow for hands-on learning - In-depth exploration of advanced features such as: - Custom entities and relationships - Advanced data integration - Security roles and permissions Ideal Skills and Experience: - Deep understanding of Power Apps and its model-driven capabilities - Experience in creating beginner-friendly tutorials - Ability to explain advanced concepts in an accessible way - Demonstrable experience with custom entities, data integration, and security roles in Power Apps - Strong ...
Looking for a figma design specialist for our project At this moment, we have built casino game project. But we are gonna to expend the project with some blockchain features. For that, we have to build figma design from scratch based on current project. So please check this project and if you have an experience in blockchain figma design, feel free to apply for this. Thank you
The song in question will be remade entirely from scratch, then shared as a project file and/or in other ways if needed.
Seeking a skilled developer to help with a Chrome extension project focused on web process automation. You will not be designing from scratch. I will pay for assistance with some initial tasks, then if you will do good work, I will have more work for you. # Required Skills: - React + TypeScript expertise - Knowledge of Chrome Extension API and Content Security Policies - Chrome Extension development experience - Experience with browser automation - Understanding of DOM manipulation - API integration knowledge - TailwindCSS proficiency # Tech Stack: - React 18 - TypeScript - Zustand (state management) - Chrome Extensions API - TailwindCSS - Vite - Git # Nice to Have: - Background in test automation # Project Scope: - Enhancing existing extension functionality - Implementing ne...
...a user-friendly backend for uploading new eMagazine issues, ideally using WordPress or a similar CMS. The site should allow for the upload of various file types, with the eMagazine displayed in an embedded flipbook format. Future improvements should be easy to implement, with potential features including blogs, forums, or subscription options. I would appreciate clear instructions or a short tutorial on how to upload eMagazines each month. Additionally, I would like the initial pages to be set up with SEO-optimized content. Ideal skills and experience for this job include: - Extensive experience with WordPress development. - Strong understanding of SEO principles and practices. - Proven track record in implementing website security measures. - Experience in creating user-frie...
I'm in need of an experienced electrical engineer to create a comprehensive load schedule for my industrial building. The load schedule should encompass: - Lighting and power outlets The building has fully detailed electrical plans, so you won't need to start from scratch. However, a deep understanding of industrial-scale electrical systems is necessary. The ideal candidate should have extensive experience in working with industrial buildings, and should be able to interpret and utilize detailed electrical schematics.
...calculations - Direct deposit processing Please note, I do not wish to entertain bids proposing to construct a payroll system from scratch. This project is for a ready-to-go solution that can be implemented immediately. The payroll will include tax tables for all 50 US states, direct deposit, and automatic tax payments to state and federal government The integration with my ERP system will be through an API. Therefore, experience in API integration is essential. Proficiency in payroll systems, ERP systems and cloud technology will greatly enhance your chances of being awarded this project. Do not submit a bid if you are going to build the payroll from scratch. Please ensure your proposal includes a detailed description of the payroll solution you are offering, including...
I'm looking for a tutorial video that demonstrates how to buy Ton Coin using the Ton Keeper app. This video is aimed at beginners, so it needs to be clear, simple, and easy to follow. Key Requirements: - The video should be a screen recording with a voiceover, guiding the viewer through each step of the process. - It should cover making a purchase in the Ton Keeper app. Ideal Skills: - Experience in creating tutorial videos, particularly for beginners. - Proficient in screen recording and voiceover work. - Familiarity with the Ton Keeper app would be a significant advantage.
I must do a web application in wordpress. It must have a landing page stile, the payment of service, so creation of account, login and payment. It must have a form plugin to do questionnaire. At th eend of the questionnaire the AI must show a report baed on answers. The web must have a form plugin jotform) The job to do: make the landing pages with information of service, add the buy pa...already create using the Ai the plugin to create the datbse but it is necessray make some changes. Other important think is create a pligin or code to create the comunication between the plugin uncanny or Ai engine. I have already installed inside the domin wordpress, jotform, uncanny, elementor, the plugin to creat ethe datbse. So you can decide to use my application to do all changes or make from sc...
I must do a web application in wordpress. It must have a landing page stile, the payment of service, so creation of account, login and payment. It must have a form plugin to do questionnaire. At th eend of the questionnaire the AI must show a report baed on answers. The web must have a form plugin jotform) The job to do: make the landing pages with information of service, add the buy pa...already create using the Ai the plugin to create the datbse but it is necessray make some changes. Other important think is create a pligin or code to create the comunication between the plugin uncanny or Ai engine. I have already installed inside the domin wordpress, jotform, uncanny, elementor, the plugin to creat ethe datbse. So you can decide to use my application to do all changes or make from sc...
I'm looking for a tutorial video that demonstrates how to buy Ton Coin using the Ton Keeper app. This video is aimed at beginners, so it needs to be clear, simple, and easy to follow. Key Requirements: - The video should be a screen recording with a voiceover, guiding the viewer through each step of the process. - It should cover making a purchase in the Ton Keeper app. Ideal Skills: - Experience in creating tutorial videos, particularly for beginners. - Proficient in screen recording and voiceover work. - Familiarity with the Ton Keeper app would be a significant advantage.
I want a person who is master in Arduino, Moisture/Humidity Sensor and Solenoid Valves of Pipes, In This project I want to integrate around 20 moisture sensor each connected to each plant and a reservoir containing water with a motor and solenoid valves leading to each plant using Arduino We can do like which plant needs water also this project should run on AC Current, when the level of water in reservoir is less it would send an alert to the user by beeping and close the motor for time being, just simple, This I want like for my home. Please if you make this it would be very kind of you because oftem I am not at home and my plants die due to lack of water
Development of advertising platform for simple game scratch voucher format, minesweeper, slot machine god, picture puzzle, bingo game, and keyboard typing game Game development that works on web and appPWA Scratch voucher format, minesweeper, slot machine god, picture puzzle, bingo game, keyboard typing game advertising platform development All games have results within 30 seconds and there is also a tournament format Only those with game-related development experience are encouraged to apply Project participation developer qualification requirements 1 Do not communicate in English. Use a translator. Development documents are not in English either 2 Only developers who can participate in development right away are encouraged to apply 3 Only those with related game developm...
I'm seeking a skilled 3D designer to create a modern outdoor meeting room, measuring 4x6. The project will include: - A seating area - A presentation screen - Lighting features - Glass windows - Outdoor seating I already have a mood board and a SketchUp file available, so you won't be starting from scratch. The final deliverables should be high-quality JPEGs, including a fully rendered lifestyle image. The design should primarily use glass, so experience with this material is crucial. A modern aesthetic is a must, as is proficiency in 3D rendering software. Looking forward to seeing your bids!
I'm seeking a professional to help me boost my Instagram presence. The primary goal is to increase the content on my page and attract more followers. Key Responsibilities: - Content Creation: Primarily, we will focus on creating engagi...Responsibilities: - Content Creation: Primarily, we will focus on creating engaging images to post on the account. - Video Production: We will also need tutorials or how-to style videos to post. Ideal Skills: - Social Media Marketing: Proven experience in Instagram marketing is crucial. - Graphic Design: Ability to create visually appealing images. - Video Editing: Skill in producing high-quality tutorial videos. - Content Strategy: Experience in devising effective strategies to increase followers. Please provide examples of your previous wo...
I need a professional to help me sharpen the icon/graphic of my logo and convert it into the necessary AI (Adobe Illustrator) vector files. Key Requirements: - Expertise in logo design and vectorization - Proficiency in Adobe Illustrator - Ability to understand and interpret verbal descriptions of design requirements - Experience creating logos and graphic elements from scratch would be beneficial I can provide a detailed description of the sharpness I am looking for, but I do not have specific reference examples. I'm open to suggestions and appreciate the expertise of the freelancer to help enhance my logo.
I'm looking for a talented graphic designer to create a series of modern, fantasy-themed scratch card images for a game. The designs need to be visually appealing and engaging to players, fitting perfectly within a fantasy context. Totally we need 12 Images
I'm looking for an expert to set up an OpenAI dashboard for me, and provide comprehensive tutorials on how to use it. Key Components: - Authentication system - Database integration - API setup The ideal freelancer should have extensive experience with OpenAI, dashboard setups, and teaching technical content in a clear and understandable manner.
...output mockup . This includes company-specific segmentation. Video Tutorial (Comprehensive): Create a step-by-step video demonstrating: Setting up Power Query, connecting to PDFs, and every stage of data transformation until the final formatted output is achieved. The tutorial should mirror the exact solution and logic used. Maintainability & Refinement: The solution should be scalable for monthly updates with new bills and adaptable to minor format changes. Payment Terms: 50% Deposit upon acceptance and receipt of the sample bills/output format. Remaining 50% released upon delivery of the working Power Query solution and the comprehensive video tutorial. Ideal Candidate: Proven Power Query exp...
I need an expert with installing Vicibox11 on a freshly setup cloud server. Ideal Skills: - Proficient in Vicibox11 installation - Experience with cloud server - Knowledgeable in server configuration Please note, the server is currently empty, hence, the freelancer will need to install the OS and configure the server from scratch.
I'm in need of a BTech professional skilled in computer languages and website development. The project is focused on creating a website and its content on a Windows operating system. Key Responsibilities: - Website creation from scratch - Developing engaging and relevant content Ideal Skills: - Proficient in computer languages, particularly those used for web development - Experience in creating websites - Content creation skills - Familiarity with Windows OS
...encountering some issues. I need Python and PostgreSQL for the project. Using the Container Manager, I was able to run containers for both Python and PostgreSQL, but I’m unable to open the project in a browser. I suspect additional configuration is required, but I’m unsure what needs to be done. The Django project is new, so the instructions should also include steps for creating a new project from scratch. I’m looking for a freelancer with relevant experience who can assist me. Specifically, I would like: A detailed installation and setup guide, including steps for creating a new Django project, as well as screenshots and step-by-step instructions. Support in case any unforeseen issues arise, preventing the project from starting. Please note: I am not lookin...
I'm looking for an expert in keyword research to help improve the search rankings of my tutorial and how-to videos on YouTube. The primary goal is to identify effective keywords that will enhance visibility and ranking on YouTube's search platform. Ideal Skills and Experience: - Proficient in YouTube SEO and keyword analysis - Experience with tutorial and how-to video optimization - Familiarity with YouTube's search algorithms - Ability to deliver actionable insights and strategies Steps: - Find keywords in VidIq, All the keywords has to scored above >70 only to be accepted - Ensure The keywords are relevant to stock market only - The keywords has to be not the one we already have here :
I'm in need of a video editor from India, specifically for beginner level 'talking head' tutorial videos. This will be a long-term project on a low budget, so please only bid if you're comfortable with a rate of 1200 INR per video. Key Requirements: - You will be editing tutorial videos, so experience in this niche is a plus. - Footage will be provided, so no shooting is needed on your part. - The editing tasks will include basic cuts and transitions, text overlays and graphics, as well as sound enhancement. Ideal Skills: - Proficiency in video editing software. - Ability to create engaging content through effective editing. - Prior experience with tutorial videos is a plus.
I'm looking for an engineer with experience in microcontrollers or Arduino to build a timer for an educational project. This timer should have the following functionalities: - Countdown Timer - Interval Timer The timer should use a Seven-segment display. Ideal candidates for this project should have a strong background in electronics and programming, particularly with Arduino or similar microcontrollers. Experience with building educational tools or projects will be a plus.
I'm looking for a talented Unity developer to create a mobile-friendly low poly 3D map for a game. The map should cover an area of 2km x 2km and include diverse areas such as a collapsed railway station, a bridge, a shipyard, three towns, a factory area, and a temple. Key Requirements: - All models (trees, grass, buildings, rails, ships, bridges, etc.) should be created from scratch, with an emphasis on low polygon counts but high-quality detailing in textures. - The aesthetic should blend a realistic feel with stylized elements. Ideal Skills: - Proficiency in Unity and 3D modeling - Experience with creating low poly models - Understanding of mobile game development requirements - Ability to create high-quality textures and details on low poly models.
I'm looking for a professional with solid experience in writing unit tests using MStest for my Asp.Net web applic...solid experience in writing unit tests using MStest for my Asp.Net web application. The project is built using VB and framework 4.8.1. Key Areas for Unit Tests: - Business Logic - Data Access Layer - User Interface I need someone to write all the unit tests from scratch. Fortunately, I have detailed documentation available for the functionalities, so you won't be starting from scratch. Ideal Skills and Experience: - Proficiency in VB and Asp.Net - Extensive experience with MStest - Ability to write comprehensive unit tests from scratch - Good understanding of business logic, data access layers and user interfaces - Familiarity with interpret...
I'm looking for a mobile app developer to create an application for monitoring data from a moisture sensor connected to an Arduino device. The app should be compatible with both iOS and Android platforms. Key Features: - Monitor data from a moisture sensor in real time - Cross-platform compatibility (iOS and Android) Ideal Skills: - Proficient in mobile app development, particularly for iOS and Android - Prior experience working with Arduino and sensor data - Strong understanding of UI/UX for sensor monitoring applications
I'm seeking a professional to help me modify an existing script for a SaaS project. The goal is to create a subscription-based service tailored for potential clients. Key requirements include: - Utilizing a ready-made developer script: I don't need a site built from scratch, but I do want a customized version of an existing script that I can control from an admin panel. - Country-specific pricing: I want the ability to target specific countries and adjust pricing based on their economic situation. This will involve creating multiple domain names for each modified version. - Future-proofing: I want to own or take a subscription this script and have the capability to control it and make modifications in the future. It'...
I am starting a new business and need to set up an automation system on WhatsApp to help manage customer interactions, order confirmations, invoicing and payment processing. Key Responsibilities: - Automate customer interactions on WhatsA...manage customer interactions, order confirmations, invoicing and payment processing. Key Responsibilities: - Automate customer interactions on WhatsApp - Confirming customer orders - Generating invoices - Managing a payment gateway Ideal Skills: - Experience with WhatsApp Business API - Knowledge in setting up payment gateways - Expertise in automation tools Please note, this is a start-from-scratch project, so creativity and problem-solving skills will be key. I am looking for a freelancer who can build a robust system tailored to my busin...
I'm in need of a seasoned back-end/full-stack developer to help me build a few APIs for my mobile app from the ground up. This project is for a startup and while it's small-scale for now, there's potential for future...Working with relational databases, specifically PostgreSQL or MySQL - Using PHP with Laravel for back-end programming I require the implementation of OAuth for authentication security, so experience with this is essential. Quality and organization are paramount; I need code that is clear, structured, and adheres to high-quality standards. After the API work, we can discuss building a website from scratch, which will not be included in the cost of this project. Please note, while the scope of this project may seem small, the potential for further de...
...private content by selling photos, videos, and live interactions directly to their subscribers. One of the most time-consuming aspects of this process is chatting with subscribers. Currently, agencies hire human chatters to engage with subscribers, build relationships, and sell content. This approach is labor-intensive and not scalable. Objective: Instead of developing a completely new AI from scratch, we want to leverage existing AI technology, such as ChatGPT’s API, and adapt it for this utility. The goal is to educate and fine-tune the ChatGPT API to perform the specific tasks of chatting, engaging, and selling content on while being fully integrated with a CRM system for easy management by agencies. About is a platform similar to OnlyFans, where creators sell