Buggy python submission (verdict: Runtime Error):
while 1:
    d, w = map(int, input().split())
    if d == w == 0:
        break
    E = [[*map(int, input().split())] for i in range(d)]
    ans = 0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    # [x1, x2] x [y1, y2]
                    co = 10**18
                    for x in range(x1, x2+1):
                        co = min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co = min(co, E[x1][y], E[x2][y])
                    ci = 0
                    cnt = 0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci = max(ci, E[x][y])
                            cnt += E[x][y]
                    if ci < co:
                        ans = max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(ans)

Fixed submission:
while 1:
    d, w = map(int, input().split())
    if d == w == 0:
        break
    E = [list(map(int, input().split())) for i in range(d)]
    ans = 0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    co = 10**18
                    for x in range(x1, x2+1):
                        co = min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co = min(co, E[x1][y], E[x2][y])
                    ci = cnt = 0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci = max(ci, E[x][y])
                            cnt += E[x][y]
                    if ci < co:
                        ans = max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(ans)

Buggy python submission (verdict: Runtime Error):
while 1:
    d, w = map(int, input().split())
    if d == w == 0:
        break
    E = [[*map(int, input().split())] for i in range(d)]
    ans = 0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    co = 10**18
                    for x in range(x1, x2+1):
                        co = min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co = min(co, E[x1][y], E[x2][y])
                    ci = 0
                    cnt = 0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci = max(ci, E[x][y])
                            cnt += E[x][y]
                    if ci < co:
                        ans = max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(ans)

Fixed submission:
while 1:
    d, w = map(int, input().split())
    if d == w == 0:
        break
    E = [list(map(int, input().split())) for i in range(d)]
    ans = 0
    for x2 in range(d):
        for y2 in range(w):
            for x1 in range(x2-1):
                for y1 in range(y2-1):
                    co = 10**18
                    for x in range(x1, x2+1):
                        co = min(co, E[x][y1], E[x][y2])
                    for y in range(y1, y2+1):
                        co = min(co, E[x1][y], E[x2][y])
                    ci = cnt = 0
                    for x in range(x1+1, x2):
                        for y in range(y1+1, y2):
                            ci = max(ci, E[x][y])
                            cnt += E[x][y]
                    if ci < co:
                        ans = max(ans, (x2-x1-1)*(y2-y1-1)*co - cnt)
    print(ans)