#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int main()
{
    int a[16][16], n, m, i, j, sum=0;
    f>>n>>m;
    for (i=1; i<=n; i++){
            sum=0;
        for (j=1; j<=m; j++)
        {
            f>>a[i][j];
            sum+=a[i][j];
        }
        if (sum < 0)
            for (j=1; j<=m; j++)
            a[i][j]*=-1;
    }
    sum=0;
    for (j=1; j<=m; j++){
            sum=0;
    for (i=1; i<=n; i++)
    {
        sum+=a[i][j];
    }
        if (sum<0)
            for (i=1; i<=n; i++)
            a[i][j]*=-1;
    }
    sum=0;
    for (i=1; i<=n; i++)
        for (j=1; j<=m; j++)
        sum+=a[i][j];
    g<<sum;
    return 0;
}