#include <fstream>

using namespace std;
ifstream f ("flip.in");
ofstream g ("flip.out");
int r,c,a[1000][1000],s,i,j;
int main()
{
    f>>r>>c;
    for (i=1;i<=r;i++)
        for (j=1;j<=c;j++)
            f>>a[i][j];
    for (i=1;i<=r;i++)
        {
            s=0;
            for (j=1;j<=c;j++)
                s=s+a[i][j];
            if (s<-s) for (j=1;j<=c;j++) a[i][j]=-a[i][j];
        }
    for (j=1;j<=c;j++)
        {
            s=0;
            for (i=1;i<=r;i++)
                s=s+a[i][j];
            if (s<-s) for (i=1;i<=r;i++) a[i][j]=-a[i][j];
        }
    s=0;
    for (i=1;i<=r;i++)
        for (j=1;j<=c;j++)
            s=s+a[i][j];
    g<<s;
    return 0;
}