#include <iostream>
#include <vector>

using namespace std;
using ll=long long;

int main(){
    int n,m;
    cin>>n>>m;
    vector<ll> a;
    vector<vector<ll>> dp(n+1,vector<ll>(n+1,-1e15));
    ll ans=-1e15;
    dp[0][0]=0;



    for(int i=0;i<n;i++){
        ll cur=0;
        for(int j=0;j<m;j++){
            ll tmp;
            cin>>tmp;
            cur+=tmp;
        }
        a.push_back(cur);
    }

    for(int i=0;i<n;i++){
        dp[i+1][0]=0;
        for(int j=1;j<=n;j++){
            if(j%2){
                dp[i+1][j]=max(dp[i][j],dp[i][j-1]+a[i]);
            }else{
                dp[i+1][j]=max(dp[i][j],dp[i][j-1]-a[i]);
            }
            ans=max(ans,dp[i+1][j]);
        }
    }
    cout<<ans<<endl;

    return 0;
}