#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
typedef long long ll;
typedef unsigned long long ull;
const int MAX = 1e9;
const int MIN = -1*1e9;
const ll MAXLL = 1e18;
const ll MINLL = -1*1e18;
//const ll MOD = 998244353;
//const ll MOD = 1000000007;
int main()
{
    ll N,M; cin >> N >> M;
    vector<ll> V(N);
    for(int i = 0; i < N; i++)
    {
        for(int j = 0; j < M; j++)
        {
            ll A; cin >> A;
            V[i] += A;
        }   
    }

    vector<vector<ll>> DP(N+1,vector<ll>(2,MINLL));
    DP[0][0] = 0;

    for(int i = 0; i < N; i++)
    {
        DP[i+1][0] = max({DP[i+1][0],DP[i][0],DP[i][1]-V[i]});
        DP[i+1][1] = max({DP[i+1][1],DP[i][1],DP[i][0]+(V[i])});
    }

    cout << max(DP[N][0],DP[N][1]) << endl;
    return 0;
}