#include <bits/stdc++.h>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");

int a[18][18], n, m;

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