R, C = list(map(int, input().split()))

A = [list(map(int, input().split())) for _ in range(R)]

dp_l = [[0]*C for _ in range(R)]

for r in range(R):

for c in range(C):

dp_l[r][c] = A[r][c]+max(dp_l[r-1][c] if r-1 >= 0 else 0, dp_l[r][c-1] if c-1 >= 0 else 0)

dp_r = [[0]*C for _ in range(R)]

for r in reversed(range(R)):

for c in reversed(range(C)):

dp_r[r][c] = A[r][c]+max(dp_r[r+1][c] if r+1 < R else 0, dp_r[r][c+1] if c+1 < C else 0)

dp_h, dp_v = [[[dp_r[0][0]]*C for _ in range(R)] for _ in range(2)]

for r in reversed(range(R)):

for c in range(C):

accu = 0

for nc in reversed(range(c+1)):

left_v = (dp_l[r-1][nc+1] if nc+1 <= c else dp_l[r-1][nc]) if r-1 >= 0 else 0

left_h = dp_l[r][nc-1] if nc-1 >= 0 else 0

right = max(dp_r[r][c+2] if c+2 < C else 0, dp_r[r+1][nc+1] if r+1 < R and nc+1 < C else 0)

dp_h[r][c] = min(dp_h[r][c], max(accu, max(left_v, left_h)+right, dp_v[r+1][nc] if r+1 < R else 0))

accu = max(accu, left_v+right)

accu = 0

for nr in range(r, R):

right_h = (dp_r[nr-1][c+1] if nr-1 >= r else dp_r[nr][c+1]) if c+1 < C else 0

right_v = dp_r[nr+1][c] if nr+1 < R else 0

left = max(dp_l[r-2][c] if r-2 >= 0 else 0, dp_l[nr-1][c-1] if nr-1 >= 0 and c-1 >= 0 else 0)

dp_v[r][c] = min(dp_v[r][c], max(accu, max(right_h, right_v)+left, dp_h[nr][c-1] if c-1 >= 0 else 0))

accu = max(accu, right_h+left)

assert(dp_h[0][C-1] == dp_v[0][C-1])