#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream intrare("flip.in");
    ofstream iesire("flip.out");
    int m,n, sumatotala = 0;
    intrare>>m>>n;
    for(int i = 1; i<=m; i++)
    {
        int suma = 0;
        for(int j = 1; j<=n; j++)
        {
            int x;
            intrare>>x;
            suma+=x;
        }
        if(suma<-suma)
            suma*=-1;

        sumatotala+=suma;
    }
    iesire<<sumatotala;

    return 0;
}