#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

const long long INF = 1LL<<60;

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n, m;
  cin >> n >> m;

  vector<vector<long long> > a(n, vector<long long>(m));
  for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++)
      cin >> a[i][j];

  vector<long long> cur(2);
  cur[1] = -INF;

  for (int i = 0; i < n; i++) {
    vector<long long> nxt(2);

    long long sum = 0;
    for (int j = 0; j < m; j++)
      sum += a[i][j];
    nxt[0] = max(cur[0], cur[1] - sum);
    nxt[1] = max(cur[1], cur[0] + sum);
    cur = nxt;
  }

  cout << max(cur[0], cur[1]) << endl;
  
  return 0;
}