#include <fstream>

using namespace std;
ifstream in("flip.in");
ofstream out("flip.out");
int main()
{
    int n, m, i, j, mat[17][17], sum_l = 0, sum_col = 0, sum_totala = 0;
    in >> n >> m;
    for(i = 1; i <= n; i++)
        for(j = 1; j <= m; j++) in >> mat[i][j];
    for(i = 1; i <= n; i++) {
        sum_l = 0;
        for(j = 1; j <= m; j++) {
            sum_l = sum_l + mat[i][j];
        }
        if(sum_l*(-1) > sum_l) {
            for(j = 1; j <= m; j++) mat[i][j] = mat[i][j] * (-1);
        }
    }
    for(j = 1; j <= m; j++) {
        sum_col = 0;
        for(i = 1; i <= n; i++) {
            sum_col = sum_col + mat[i][j];
        }
        if(sum_col * (-1) > sum_col) {
            for(i = 1; i <= n; i++) mat[i][j] = mat[i][j] * (-1);
        }
    }
    for(i = 1; i <= n; i++)
        for(j = 1; j <= m; j++) sum_totala = sum_totala + mat[i][j];
    out << sum_totala;

    return 0;
}