typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;

int main() {
    ll n,m;
    std::cin >> n>>m;
    
    vector<ll> a(n,0);
    
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            ll b;
            std::cin >> b;
            a[i] += b;
        }
    }
    
    vector<vector<ll>> dp(n+1,vector<ll>(2,0));
    
    // dp[i][1] 奇数番目状態で最大
    dp[0][0] = 0;
    dp[0][1] = -1e15;
    
    for (int i = 0; i < n; i++) {
        dp[i+1][0] = max(dp[i][0], dp[i][1]-a[i]);
        dp[i+1][1] = max(dp[i][1], dp[i][0]+a[i]);
    }
    
    std::cout << dp[n][1] << std::endl;
}