import sys
import math
import collections
import bisect
import itertools
import decimal

# import numpy as np

# sys.setrecursionlimit(10 ** 6)
INF = 10 ** 20
MOD = 10 ** 9 + 7
# MOD = 998244353

ni = lambda: int(sys.stdin.readline().rstrip())
ns = lambda: map(int, sys.stdin.readline().rstrip().split())
na = lambda: list(map(int, sys.stdin.readline().rstrip().split()))
na1 = lambda: list(map(lambda x: int(x) - 1, sys.stdin.readline().rstrip().split()))


# ===CODE===

def main():
    n, m = ns()
    mat = [na() for _ in range(n)]

    res = []
    for i in range(n):
        tmp = 0
        for j in range(m):
            tmp += mat[i][j]
        res.append(tmp)

    dp = [[0] * 2 for _ in range(n + 1)]

    ans = 0
    for i in range(n):
        for j in range(i + 1, n + 1):
            dp[j][0] = max(dp[j][0], dp[i][1] - res[j - 1])
            dp[j][1] = max(dp[j][1], dp[i][0] + res[j - 1])
            ans = max(ans, dp[j][0], dp[j][1])

    print(ans)


if __name__ == '__main__':
    main()