#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,M; cin >> N >> M;
    vector<ll> A(N, 0);
    rep(i,N)rep(j,M){ ll a; cin >> a; A[i] += a; }
    
    ll dp0 = 0, dp1 = -1e18;
    rep(i,N) tie(dp0, dp1) = make_pair(max(dp0, dp1 - A[i]), max(dp1, dp0 + A[i]));
    cout << max(dp0, dp1) << endl;
}