#include <fstream>

std::ifstream in("flip.in");
std::ofstream out("flip.out");

int v[16][16], n, m;

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

    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++) in >> v[i][j];

    while (true) {
        bool stop = true;
        for (int i = 0; i < n; i++) {
            int sum = 0;
            for (int j = 0; j < m; j++) {
                sum += v[i][j];
            }

            if (sum < 0) {
                stop = false;
                for (int j = 0; j < m; j++) {
                    v[i][j] *= -1;
                }
            }
        }

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

            if (sum < 0) {
                stop = false;
                for (int i = 0; i < n; i++) {
                    v[i][j] *= -1;
                }
            }
        }

        if (stop) break;
    }

    int sum = 0;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++) sum += v[i][j];

    out << sum;
}