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

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

const int DIM = 20;
int a[DIM][DIM];
int n, m;

int main()
{
    fin >> n >> m;

    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            fin >> a[i][j];

    int suma(0);

    for (int i = 1; i <= n; ++i)
    {
        suma = 0;

        for (int j = 1; j <= m; ++j)
            suma += a[i][j];

        if (suma < -1 * suma)
            for (int j = 1; j <= m; ++j)
                a[i][j] *= (-1);
    }

    for (int j = 1; j <= m; ++j)
    {
        suma = 0;

        for (int i = 1; i <= n; ++i)
            suma += a[i][j];

        if (suma < -1 * suma)
            for (int i = 1; i <= n; ++i)
                a[i][j] *= (-1);
    }

    suma = 0;

    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            suma += a[i][j];

    fout << suma;

    return 0;
}