#include <fstream>

using namespace std;

ifstream cin("filip.in");
ofstream cout("filip.out");

typedef long long ll;
const int maxnm = 16;

int a[maxnm + 1][maxnm + 1];
int main() {
    int n,m,i,j;
    int sum;
    cin >> n >> m;
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++)
            cin >> a[i][j];

    // linii
    for (i = 1; i <= n; i++) {
        sum = 0;
        for (j = 1; j <= m; j++)
            sum += a[i][j];
        if (sum < 0) {
            // flip
            for (j = 1; j <= m; j++)
                a[i][j] *= -1;
        }
    }

    // coloane
    for (j = 1; j <= m; j++) {
        sum = 0;
        for (i = 1; i <= n; i++)
            sum += a[i][j];
        if (sum < 0) {
            // flip
            for (i = 1; i <= n; i++)
                a[i][j] *= -1;
        }
    }

    // suma totala
    ll sumt=0;
    for (i = 1; i <= n; i++)
        for (j = 1; j <= m; j++)
            sumt += a[i][j];

    cout << sumt;

    return 0;
}