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)

    start = -1
    for i in range(1, n):
        if res[i] < res[i - 1]:
            start = i-1
            break
    if start == -1:
        print(res[-1])
        exit(0)

    ans = res[start]
    minimum = res[start]
    flg = 0  # 0:kudari 1:nobori
    for i in range(start + 1, n):
        if flg == 0:
            if res[i] <= minimum:
                minimum = res[i]
            else:
                flg = 1
        else:
            if res[i] >= res[i - 1]:
                continue
            else:
                ans += res[i - 1] - minimum
                minimum = res[i]
                flg = 0

    if flg == 1:
        ans += res[-1] - minimum
    print(ans)

if __name__ == '__main__':
    main()