# pre-conditions-start

Requires(((0) <= (x)) and ((0) <= (y)))

# pre-conditions-end

# post-conditions-start

Ensures(((Result()) == (-1)) or (((Result()) >= (x)) and ((Result()) <= (y))))

Ensures(((Result()) == (-1)) or (((Result() % 2)) == (0)))

Ensures(((Result()) == (-1)) or (Forall(int, lambda d_0_i_:

not ((((x) <= (d_0_i_)) and ((d_0_i_) <= (y))) and (((d_0_i_ % 2)) == (0))) or ((Result()) >= (d_0_i_)))))

Ensures(((Result()) == (-1)) == ((x) >= (y)))

# post-conditions-end

# impl-start

num : int = -1

if (x) >= (y):

return num

if ((x % 2)) == (0):

num = x

elif True:

num = (x) + (1)

d_1_i_ : int = (x) + (2)

while (d_1_i_) <= (y):

# invariants-start

Invariant(((d_1_i_) >= (x)) and ((d_1_i_) <= ((y) + (1))))

Invariant(((num) == (-1)) or (((num % 2)) == (0)))

Invariant(Forall(int, lambda d_2_j_:

not ((((x) <= (d_2_j_)) and ((d_2_j_) < (d_1_i_))) and (((d_2_j_ % 2)) == (0))) or ((num) >= (d_2_j_))))

Invariant(((num) == (-1)) or (((num) >= (x)) and ((num) < (d_1_i_))))

# invariants-end

if ((d_1_i_ % 2)) == (0):

num = d_1_i_

d_1_i_ = (d_1_i_) + (1)

return num