#include <fstream>
using namespace std;

int n, m, a[21][21];
int sum;

void Citire() {
    int i, j;
    ifstream f("flip.in");
    f >> n >> m;
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++)
            f >> a[i][j];
    f.close();
}

void Prelucrare() {
    int i, j, S;
    for (i = 1; i <= n; i++) {
        S = 0;
        for (j = 1; j <= m; j++)
            S += a[i][j];
        if (S < 0)
            for (j = 1; j <= m; j++)
                a[i][j] *= -1;
    }
    for (j = 1; j <= m; j++) {
        S = 0;
        for (i = 1; i <= n; i++)
            S += a[i][j];
        if (S < 0)
            for (i = 1; i <= n; i++)
                a[i][j] *= -1;
    }
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++)
            sum += a[i][j];
}

void Afisare() {
    ofstream g("flip.out");
    g << sum;
    g.close();
}

int main() {
    Citire();
    Prelucrare();
    Afisare();
    return 0;
}