#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int i,j,n,m,joc[17][17],sump,sumn,sumf;
int main()
{
    f>>n>>m;
    for (i=1;i<=n;++i)
        for (j=1;j<=m;++j)
            f>>joc[i][j];
    for (i=1;i<=n;++i)
    {
        sump=sumn=0;
        for (j=1;j<=m;++j)
        {
            if (joc[i][j]>0)
                sump+=joc[i][j];
            else
                sumn+=joc[i][j];
            if (sump<-sumn)
                for (j=1;j<=m;++j)
                    joc[i][j]=-joc[i][j];
        }
    }
    for (i=1;i<=m;++i)
    {
        sump=sumn=0;
        for (j=1;j<=n;++j)
        {
            if (joc[j][i]>0)
                sump+=joc[j][i];
            else
                sumn+=joc[j][i];
            if (sump<-sumn)
                for (j=1;j<=n;++j)
                    joc[j][i]=-joc[j][i];
        }
    }
    for (i=1;i<=n;++i)
        for (j=1;j<=m;++j)
            sumf+=joc[i][j];
    g<<sumf;
}