#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");

int main()
{
    int n, m, a[16][16], s, i, j;
    
    fin >> n >> m;

    for(i = 0; i < n; ++i)
    {
        for(j = 0 ; j < m; ++j)
        {
            fin >> a[i][j];
        }
    }
 
    for(i = 0; i < n; ++i)
    {
        s = 0;
        for(j = 0; j < m; ++j)
        {
            s += a[i][j];
        }
        if(s < 0)
        {
            for(j = 0; j < m; ++j)
            {
                a[i][j] = (-1) * a[i][j];
            }
        }
    }

    for(j = 0; j < m; ++j)
    {
        s = 0;
        for(i = 0; i < n; ++i)
        {
            s += a[i][j];
        }
        if(s < 0)
        {
            for(i = 0; i < n; ++i)
            {
                a[i][j] = (-1) * a[i][j];
            }
        }
    }

    s = 0;

    for(i = 0; i < n; ++i)
    {

        for(j = 0 ; j < m; ++j)
        {
            s += a[i][j];
        }
    }

    fout << s;

    return 0;
}