#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define rep(i, n) for (int i = 0; i < (n); i++)
#define P pair<int, int>

void chmax(ll& a, ll b) {
  if (a < b) a = b;
}

int main() {
  int n, m;
  cin >> n >> m;

  vector<ll> a(m), sum(n);

  rep(i, n) {
    rep(j, m) {
      cin >> a[j];
      sum[i] += a[j];
    }
  }


  ll dp[n+1][2] = {0};

  rep(i, n) {
    chmax(dp[i+1][1], dp[i][1]);
    chmax(dp[i+1][0], dp[i][0]);
    chmax(dp[i+1][1], dp[i][0] + sum[i]);
    chmax(dp[i+1][0], dp[i][1] - sum[i]);
  }

  cout << max(dp[n][0], dp[n][1]) << endl;

}