#include <bits/stdc++.h>
using namespace std;


int main() {
    
int N;
int M;
long long int Ans=0LL;
int Eat=0;

cin >> N >> M ;
vector<long long int>Happiness(N+1);
vector<long long int>happy(M);

for(int i=1; i<N+1; i++){
    for(int j=0; j<M; j++){
        cin >> happy.at(j);
        Happiness.at(i)=Happiness.at(i)+happy.at(j);
        happy.at(j)=0LL;
    }
}

for(int i=1; i<N; i++){
    if(Eat%2==0){
        if(Happiness.at(i)>Happiness.at(i+1)){
            Eat++;
            Ans=Ans+Happiness.at(i);
        }
    }
    else{
        if(Happiness.at(i)<Happiness.at(i+1)){
            Eat++;
            Ans=Ans-Happiness.at(i);
        }
    }
}
if(Eat%2==0){
    Ans=Ans+Happiness.at(N);
}



cout << Ans ; 


}