#include <fstream>

using namespace std;

int main()
{
    long a[16][16],s=0;
    int n,m,o=1;
    ifstream f("flip.in");
    ofstream g("flip.out");
    f>>n>>m;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            f>>a[i][j];
    while (o==1)
    {
        o=0;
        for (int i=1;i<=n;i++)
        {
            for (int j=1;j<=m;j++)
                s+=a[i][j];
            if (s<0)
            {
                for (int j=1;j<=m;j++)
                    a[i][j]*=-1;
                o=1;
            }
            s=0;
        }
        for (int j=1;j<=m;j++)
        {
            for (int i=1;i<=n;i++)
                s+=a[i][j];
            if (s<0)
            {
                for (int i=1;i<=n;i++)
                    a[i][j]*=-1;
                o=1;
            }
            s=0;
        }
    }
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            s+=a[i][j];
    g<<s;

}