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

ifstream is("flip.in");
ofstream os("flip.out");

int n, m, x, maxim, minim, suma;
int v[17][17];
int l[17], c[17];


int main()
{
    is >> n >> m;
    for(int i = 1; i <= n; ++i)
    {
        for(int j = 1; j <= m; ++j)
        {
            is >> v[i][j];
            suma += v[i][j];
        }
        if (suma < 0)
        {
            for(int j = 1; j <= m; ++j)
            {
                 v[i][j] *= -1;
            }
        }
        suma = 0;
    }
    for(int j = 1; j <= m; ++j)
    {
        for(int i = 1; i<= n; ++i)
            suma += v[i][j];
        if(suma < 0)
            for(int i = 1; i<= n; ++i)
            {
                v[i][j] *= -1;
            }
        suma = 0;
    }
    suma = 0;
    for(int i = 1; i <= n; ++i)
    {
        for(int j = 1; j <= m; ++j)
        {
             suma += v[i][j];
        }
    }
    os << suma;
    is.close();
    os.close();
    return 0;
}