#include <iostream>
#include <fstream>
using namespace std;

int main()
{ifstream f("flip.in");
    ofstream g("flip.out");
    int m,n,i,j,s,a[20][16],k;
    f>>n>>m;
    for (i=1;i<=n;i++)
        {
            s=0;

        for (j=1;j<=m;j++)
            {f>>a[i][j];
            s+=a[i][j];

            }
            if (s<0)
              for (k=1;k<=m;k++)
              a[i][k]=a[i][k] *-1;
        }

        for(j=1;j<=m;j++)
        {
            s=0;
            for (i=1;i<=n;i++)
                s=s+a[i][j];
             if (s<0)
              for (k=1;k<=n;k++)
                a[k][j]=a[k][j]*-1;
        }

            s=0;
        for (i=1;i<=n;i++)
            for (j=1;j<=m;j++)
                s+=a[i][j];

                g<<s;
    return 0;
}