#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int main () {
    int n, m, flip[16][16];
    f >> n >> m;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            f >> flip[i][j];
        }
    }

    int sum_p, sum_n;
    for (int i = 0; i < n; i++) {
        sum_p = 0;
        sum_n = 0;
        for (int j = 0; j < m; j++) {
            if (flip[i][j] < 0) {
                sum_n += (-flip[i][j]);
            } else {
                sum_p += flip[i][j];
            }
        }
        if (sum_n > sum_p) {
            for (int j = 0; j < m; j++) {
                flip[i][j] *= (- 1);
            }
        }
    }

    for (int j = 0; j < m; j++) {
        sum_p = 0;
        sum_n = 0;
        for (int i = 0; i < n; i++) {
            if (flip[i][j] < 0) {
                sum_n += (-flip[i][j]);
            } else {
                sum_p += flip[i][j];
            }
        }
        if (sum_n > sum_p) {
            for (int i = 0; i < n; i++) {
                flip[i][j] *= (- 1);
            }
        }
    }

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

    g << sum;
}