#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int a[17][17],n,m,i,j,s,S,Vl[10],Vc[10],nr,nr2;
int main()
{
    f >> n >> m;
    for (i=1;i<=n;i++)
        for (j=1;j<=m;j++) f >> a[i][j];
    for (i=1;i<=n;i++)
    {
        s=0;
        for (j=1;j<=m;j++) s+=a[i][j];
        if (s<0) Vl[++nr]=i;
    }
     for (i=1;i<=nr;i++)
    {
        for (j=1;j<=n;j++) a[Vl[i]][j]*=-1;
    }
    for (j=1;j<=m;j++)
    {
        s=0;
        for (i=1;i<=m;i++) s+=a[i][j];
        if (s<0) Vc[++nr2]=j;
    }
    for (j=1;j<=nr2;j++)
    {
        for (i=1;i<=n;i++) a[i][Vc[j]]*=-1;
    }
    for (i=1;i<=n;i++)
        for (j=1;j<=m;j++) S+=a[i][j];
    g << S;
    return 0;
}