#include <fstream>
using namespace std;


int main()
{
    ofstream g("flip.out");
    ifstream f("flip.in");
    int a[16][16], n, m, i, j, sump, sumn;

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


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

        for (j = 0; j < m; j++)
        {
            if (a[i][j] > 0)
                sump += a[i][j];
            else sumn+= -a[i][j];
        }

        if (sumn > sump)
        {
            for (j = 0; j < m; j++)
                a[i][j] = -a[i][j];
        }
    }

    for (j = 0; j < m; j++)
    {
        sump = 0;
        sumn = 0;
        for (i = 0; i < n; i++)
        {
            if (a[i][j] > 0)
                sump += a[i][j];
            else sumn += -a[i][j];
        }
        if (sumn > sump)
        {
            for (i = 0; i < n; i++)
            {
                a[i][j] = -a[i][j];
            }
        }
    }
    int sum = 0;
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
        {
            sum += a[i][j];
        }
    }
    g << sum;
    f.close();
    g.close();

    return 0;
}