#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream f("flip.in");
    ofstream g("flip.out");

    long long n, m, a[1000][16];

    f >> n >> m;

    if (n >= 1 && m <= 16)
    {
        for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            f >> a[i][j];
        }
    }
    }
    else throw "error";
    

    int suma = 0;


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

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

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

    for (int j = 0; j < m; j++)
    {
        int s = 0;

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

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

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

    g << suma;

    return 0;
}