#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream in("flip.in");
    ofstream out("flip.out");

    int n, m, d[17][17], sp=0, sn=0, i, j;

    in>>n;
    in>>m;
    for(i=1;i<=n;i++){

    for(j=1;j<=m;j++){
    in>>d[j][i];

if(d[j][i]>=0)
sp += d[j][i];
else
sn = sn+d[j][i];
    }

    }

if(sp>=sn && sp!=0)
out<<sp;
else
out<<sn;
    return 0;
}