#include <iostream>
#include <fstream>
using namespace std;
int m,n,x[50][50],i,j,k,s;
int main()
{
    ifstream f("flip.in");
    ofstream g("flip.out");
    f >> m;
    f >> n;
    for (i=1;i<=m;++i)
    {
        s=0;
        for (j=1;j<=n;++j)
        {
            f >> x[i][j];
            s=s+x[i][j];
        }
    if (s<0)
        for (k=1;k<=n;++k)
            x[i][k]=-x[i][k];
    }
        for (i=1;i<=n;++i)
    {
        s=0;
        for (j=1;j<=m;++j)
        {
            s=s+x[j][i];
        }
    if (s<0)
        for (k=1;k<=m;++k)
            x[k][i]=-x[k][i];
    }
    s=0;
    for (int i=1;i<=m;++i)
        for (int j=1;j<=n;++j)
                s=s+x[i][j];
    g << s;
    return 0;
}