#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <set>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;

int main() {
  int N, M;
  cin >> N >> M;

  vector<ll> sum(N, 0);
  ll a;
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < M; ++j) {
      cin >> a;
      sum[i] += a;
    }
  }

  ll dp[N + 1][2];
  memset(dp, 0, sizeof(dp));

  for (int i = 0; i < N; ++i) {
    ll s = sum[i];
    dp[i + 1][0] = max(dp[i + 1][0], max(dp[i][0], dp[i][1] - s));
    dp[i + 1][1] = max(dp[i + 1][1], max(dp[i][1], dp[i][0] + s));
  }

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

  return 0;
}