#include <fstream>
using namespace std;
ifstream cin("flip.in");
ofstream cout("flip.out");
long long b, x, y, r, s, i, j, m, n, k;
int a[20][20], sc[20], sl[20];
int main () {
    cin>>n>>m;
    for (i = 1;i <= n;i++) {
        for (j = 1;j <= m;j++) {
            cin>>a[i][j];
        }
    }
    for (i = 1;i <= n;i++) {
        for (j = 1;j <= m;j++) {
            sl[i] += a[i][j];
        }
        if(sl[i] < 0) {
            for (k = 1;k <= m;k++) {
                a[i][k] = a[i][k] * -1;
            }
        }
    }
    for (j = 1;j <= m;j++) {
        for (i = 1;i <= n;i++) {
            sc[j] += a[i][j];
        }
        if(sc[j] < 0) {
            for (k = 1;k <= n;k++) {
                a[k][j] *= -1;
            }
        }
    }
    for (i = 1;i <= n;i++) {
        for (j = 1;j <= m;j++)
            s += a[i][j];
    }
    cout<<s;
}