#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;
const int INF = 100100100;

int main(){
    int n , m;
    cin >> n >> m;
    vector<ll> a(n + 1 , 0);
    for(int i = 1; i <= n; i++){
        for(int j = 0; j < m; j++){
            ll now;
            cin >> now;
            a[i] += now;
        }
    }
    vector<vector<ll>> dp(n + 10 , vector<ll>(2 , 0));
    for(int i = 1; i <= n; i++){
        dp[i][1] = max({dp[i - 1][1] , dp[i - 1][0] + a[i] , a[i]});
        dp[i][0] = max(dp[i - 1][0] , dp[i - 1][1] - a[i]);
    }
    cout << max(dp[n][1] , dp[n][0]) << endl;
    return 0;
}