#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000000000;
int main(){
  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> S(N, 0);
  for (int i = 0; i < N; i++){
    for (int j = 0; j < M; j++){
      S[i] += A[i][j];
    }
  }
  vector<vector<long long>> dp(N + 1, vector<long long>(2, -INF));
  dp[0][0] = 0;
  for (int i = 0; i < N; i++){
    dp[i + 1][0] = max(dp[i][0], dp[i][1] - S[i]);
    dp[i + 1][1] = max(dp[i][1], dp[i][0] + S[i]);
  }
  cout << max(dp[N][0], dp[N][1]) << endl;
}