#include <fstream>
using namespace std;

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

int n, m, a[17][17];

void flip(int x, int y) {
    if(x)
        for(int i = 1; i <= m; ++i)
            a[x][i] *= -1;
    if(y)
        for(int i = 1; i <= n; ++i)
            a[i][y] *= -1;
}

int sum() {
    int s = 0;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= n; ++j)
            s += a[i][j];
    return s;
}

int main() {
    fin >> n >> m;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            fin >> a[i][j];

    int max = sum();

    for(int i = 0; i <= n; ++i)
        for(int j = 0; j <= m; ++j) {
            flip(i, j);
            if(sum() > max)
                max = sum();
            flip(i, j);
        }
    fout << max;
}