#include <bits/stdc++.h>
using namespace std;
int main() {
    ifstream fin("flip.in");
    ofstream fout("flip.out");
    int n, m, i, j, v[17][17], s1, s2, s = 0;
    fin >> n >> m;
    for (i = 1; i <= n; i++)
    {
        s1 = s2 = 0;
        for (j = 1; j <= m; j++)
        {
            fin >> v[i][j];
            if (v[i][j] >= 0)
                s1 = s1 + v[i][j];
            else
                s2 = s2 + v[i][j];
        }
        if (s1 < abs(s2))
            for (j = 1; j <= m; j++)
                v[i][j] = v[i][j] * -1;
    }
    for (j = 1; j <= m; j++)
    {
        s1 = s2 = 0;
        for (i = 1; i <= n; i++)
        {
            if (v[i][j] >= 0)
                s1 += v[i][j];
            else
                s2 += v[i][j];
        }
        if (s1 < abs(s2))
            for (i = 1; i <= n; i++)
                v[i][j] *= -1, s = s + v[i][j];
        else
            for (i = 1; i <= n; i++)
                s = s + v[i][j];
    }
    fout << s;
    return 0;
}