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

int main() {
    int a, b, suma_linie = 0, suma_coloana = 0, suma = 0;

    ifstream file("flip.in");

    ofstream file2("flip.out");

    file >> a >> b;

    int matrice[a][b];

    for(int i = 0; i < a; i++) {
        for(int j = 0; j < b; j++) {
            file >>  matrice[i][j];
        }
    }

    for(int i = 0; i < a; i++) {
        for(int j = 0; j < b; j++) {
            suma_linie += matrice[i][j];
            suma_coloana += matrice[j][i];
        }

        if(suma_coloana < 0) {
            for(int j = 0; j < a; j++) {
                matrice[j][i] *= -1;
            }
        }

        if(suma_linie < 0) {
            for(int j = 0; j < b; j++) {
                matrice[i][j] *= -1;
            }
        }

        suma_linie = 0;
        suma_coloana = 0;
    }


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

    file2 << suma;
}