# include <fstream>
using namespace std;
ifstream in("flip.in");
ofstream out("flip.out");
int v[17][17];
int main()
{
    int x,n,m,i,j,sum,dif,nr,tot=0;
    in>>n>>m;
    for (i=1;i<=n;i++)
    {
        sum=dif=0;
        for (j=1;j<=m;j++)
        {
            in>>v[i][j];
            if (v[i][j]>0) sum+=v[i][j];
            else dif+=-v[i][j];
        }
        if (dif-sum>sum-dif) for (j=1;j<=m;j++) v[i][j]=-v[i][j];
    }
    for (j=1;j<=m;j++)
    {
        sum=dif=0;
        for (i=1;i<=n;i++)
        {
            if (v[i][j]>0) sum+=v[i][j];
            else dif+=-v[i][j];
        }
        if (dif-sum>sum-dif) for (i=1;i<=n;i++) v[i][j]=-v[i][j];
    }
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++) tot+=v[i][j];
    }
    out<<tot;
    return 0;
}