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

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

int n, m, a[17][17], test;

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

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            fin >> a[i][j];
        }
    }
// Verific coloana daca exista o suma mai mica decat 0. Inmultesc cu -1 daca este adevarat.
    for (int j = 1; j <= m; j++) {
        int sum = 0;
        for (int i = 1; i <= n; i++) {
            sum += a[i][j];
        }
        if (sum < 0) {
            for (int i = 1; i <= n; i++) {
                a[i][j] = a[i][j] * -1;
            }
        }
    }
// Verific linia daca exista o suam mai mica decat 0.
    for (int i = 1; i <= n; i++) {
        int sum = 0;
        for (int j = 1; j <= m; j++) {
            sum += a[i][j];
        }
        if (sum < 0) {
            for (int j = 1; j <= m; j++) {
                a[i][j] = a[i][j] * -1;
            }
        }
    }
// Resultat
    int sum = 0;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            sum += a[i][j];
        }
    }
    fout << sum;
    return 0;
}