#include <iostream>
#include <fstream>
using namespace std;
int v[20][20];
int main()
{
    ifstream in("flip.in");
    ofstream out("flip.out");
    int n,m;
    in>>n>>m;
    int i,j;
    int s=0;
    int M=0;
    for (i=1;i<=n;i++)
    {
        s=0;
        for (j=1;j<=m;j++)
        {
            in>>v[i][j];
            s=s+v[i][j];
        }
        if (s<0)
        {
            s=0;
            for (j=1;j<=m;j++)
            {
                v[i][j]*=-1;
                s=s+v[i][j];
            }
        }
    }
    for (j=1;j<=m;j++)
    {
        s=0;
        for (i=1;i<=n;i++)
        {
            s=s+v[i][j];
        }
        if (s<0)
        {
            s=0;
            for (i=1;i<=n;i++)
            {
                v[i][j]*=-1;
                s=s+v[i][j];
            }
        }
    }
    for (i=1;i<=n;i++)
    {
        for (j=1;j<=m;j++)
        {
            M+=v[i][j];
        }
    }
    out<<M;

}