/**
 *   @FileName	a.cpp
 *   @Author	kanpurin
 *   @Created	2020.08.29 15:36:38
**/

#include "bits/stdc++.h" 
using namespace std; 
typedef long long ll;

int main() {
    int n,m;cin >> n >> m;
    vector<ll> a(n);
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            ll b;cin >> b;
            a[i] += b;
        }
    }
    constexpr long long LLINF = 1e18 + 1;
    vector<vector<ll>> dp(n+1,vector<ll>(2,-LLINF));
    dp[0][1] = 0;
    ll one_max = 0, zero_max = -LLINF;
    for (int i = 0; i < n; i++) {
        dp[i + 1][0] = one_max + a[i];
        dp[i + 1][1] = zero_max - a[i];
        one_max = max(one_max,dp[i + 1][1]);
        zero_max = max(zero_max,dp[i + 1][0]);
    }
    cout << zero_max << endl;
    return 0;
}