/* -*- coding: utf-8 -*-
 *
 * 1199.cc:  No.1199 お菓子配り-2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_M = 1000;
const long long LINF = 1LL << 62;

/* typedef */

typedef long long ll;

/* global variables */

ll dp[MAX_N + 1][2];

/* subroutines */

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  dp[0][0] = -LINF;
  dp[0][1] = 0;

  for (int i = 0; i < n; i++) {
    ll asum = 0;
    for (int j = 0; j < m; j++) {
      ll aij;
      scanf("%lld", &aij);
      asum += aij;
    }

    dp[i + 1][0] = max(dp[i][0], dp[i][1] + asum);
    dp[i + 1][1] = max(dp[i][1], dp[i][0] - asum);
  }

  printf("%lld\n", max(dp[n][0], dp[n][1]));
  return 0;
}