Buggy python submission (verdict: Time Limit Exceeded):
from itertools import product

H, W = map(int, input().split())
grid_A = [list(map(int, input().split())) for _ in range(H)]
grid_B = [list(map(int, input().split())) for _ in range(H)]
diff = []
M = 0
for A, B in zip(grid_A, grid_B):
    temp = [abs(a - b) for a, b in zip(A, B)]
    M = max(max(temp), M)
    diff.append(temp)
dp = [[[False]*((H+W)*(M+1)) for _ in range(W)] for _ in range(H)]
dp[0][0][diff[0][0]] = True
for i, j in product(range(H), range(W)):
    for m in range((H+W)*(M+1)):
        if dp[i][j][m]:
            if i + 1 < H:
                d = diff[i+1][j]
                dp[i+1][j][m + d] = True
                dp[i+1][j][abs(m - d)] = True
            if j + 1 < W:
                d = diff[i][j+1]
                dp[i][j+1][m + d] = True
                dp[i][j+1][abs(m - d)] = True
for i in range((H+W)*(M+1)):
    if dp[H-1][W-1][i]:
        print(i)
        break

Fixed submission:
from itertools import product

def offset(a, b):
    result = 0
    if b == 0: return 0
    for i in range(b+1):
        if (a >> i) & 1:
            result |= (1 << b) >> i
    return result

H, W = map(int, input().split())
diff = [list(map(int, input().split())) for _ in range(H)]
M = 80
for i in range(H):
    B = list(map(int, input().split()))
    for j in range(W):
        diff[i][j] = abs(diff[i][j] - B[j])
dp = [[0]*W for _ in range(H)]
dp[0][0] = 1 << diff[0][0]
for i, j in product(range(H), range(W)):
    if (i, j) == (H-1, W-1): break
    if i+1 < H:
        k = diff[i+1][j]
        dp[i+1][j] |= (dp[i][j] >> k) | (dp[i][j] << k) | (offset(dp[i][j], k))
    if j+1 < W:
        k = diff[i][j+1]
        dp[i][j+1] |= (dp[i][j] >> k) | (dp[i][j] << k) | (offset(dp[i][j], k))
ans = dp[H-1][W-1]
print((ans & -ans).bit_length() - 1)

Buggy python submission (verdict: Time Limit Exceeded):
from itertools import product

H, W = map(int, input().split())
grid_A = [list(map(int, input().split())) for _ in range(H)]
grid_B = [list(map(int, input().split())) for _ in range(H)]
diff = []
M = 0
for A, B in zip(grid_A, grid_B):
    temp = [abs(a - b) for a, b in zip(A, B)]
    M = max(max(temp), M)
    diff.append(temp)
dp = [[[False]*((H+W)*(M+1)) for _ in range(W)] for _ in range(H)]
dp[0][0][diff[0][0]] = True
for i, j in product(range(H), range(W)):
    for m in range((H+W)*(M+1)):
        if dp[i][j][m]:
            if i + 1 < H:
                d = diff[i+1][j]
                dp[i+1][j][m + d] = True
                dp[i+1][j][abs(m - d)] = True
            if j + 1 < W:
                d = diff[i][j+1]
                dp[i][j+1][m + d] = True
                dp[i][j+1][abs(m - d)] = True
for i in range((H+W)*(M+1)):
    if dp[H-1][W-1][i]:
        print(i)
        break

Fixed submission:
from itertools import product

def offset(a, b):
    result = 0
    if b == 0: return 0
    for i in range(b+1):
        if (a >> i) & 1:
            result |= (1 << b) >> i
    return result

H, W = map(int, input().split())
diff = [list(map(int, input().split())) for _ in range(H)]
M = 80
for i in range(H):
    B = list(map(int, input().split()))
    for j in range(W):
        diff[i][j] = abs(diff[i][j] - B[j])
dp = [[0]*W for _ in range(H)]
dp[0][0] = 1 << diff[0][0]
for i, j in product(range(H), range(W)):
    if (i, j) == (H-1, W-1): break
    if i+1 < H:
        k = diff[i+1][j]
        dp[i+1][j] |= (dp[i][j] >> k) | (dp[i][j] << k) | (offset(dp[i][j], k))
    if j+1 < W:
        k = diff[i][j+1]
        dp[i][j+1] |= (dp[i][j] >> k) | (dp[i][j] << k) | (offset(dp[i][j], k))
ans = dp[H-1][W-1]
print((ans & -ans).bit_length() - 1)