#include <fstream>
using namespace std;

int a[1001][1001];
ifstream cin("flip.in");
ofstream cout("flip.out");

int main() {
    int n, m;
    cin >> n >> m;


    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> a[i][j];
        }
    }

    for (int i = 0; i < n; i++) {
        int linSum = 0;
        for (int j = 0; j < m; j++) {
            linSum += a[i][j];
        }
        if (linSum < 0) {
            for (int j = 0; j < m; j++) {
                a[i][j] = -a[i][j];
            }
        }
    }

    for (int j = 0; j < m; j++) {
        int colSum = 0;
        for (int i = 0; i < n; i++) {
            colSum += a[i][j];
        }
        if (colSum < 0) {
            for (int i = 0; i < n; i++) {
                a[i][j] = -a[i][j];
            }
        }
    }

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

    cout << sumTot << endl;

    return 0;
}