#include <fstream>

using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");

int main() {
    int a[16][16], i, j, n, m, s_j, s_i, s = 0;
    fin >> n >> m;
    for (i = 0; i < n; i++)
        for (j = 0; j < m; j++)
            fin >> a[i][j];
    //
    for (i = 0; i < n; i++) {
        s_i = 0;
        for (j = 0; j < m; j++)
            s_i += a[i][j];
        if (s_i < 0)
            for (int k = 0; k < m; k++)
                a[i][k] *= -1;
    }
    //
    for (j = 0; j < m; j++) {
        s_j = 0;
        for (i = 0; i < n; i++)
            s_j += a[i][j];
        if (s_j < 0)
            for (int k = 0; k < n; k++)
                a[k][j] *= -1;
    }
    /*
    for(i=0; i<n; i++) {
        for (j = 0; j < m; j++)
            fout << a[i][j] << " ";
        fout << '\n';
    }
    */
    for (i = 0; i < n; i++)
        for (j = 0; j < m; j++)
            s += a[i][j];
    fout << s;
    return 0;
}