#include <fstream>
using namespace std;

ifstream is("flip.in");
ofstream os("flip.out");

int a[18][18], slin[18], scol[18];
int n, m, s;

int main()
{
    is >> n >> m;
    for ( int i = 1; i <= n; i++ )
        for ( int j = 1; j <= m; j++ )
        {
            is >> a[i][j];
            slin[i] += a[i][j];
            scol[j] += a[i][j];
        }
    for ( int i = 1; i <= n; i++ )
        if ( slin[i] < 0 )
            for ( int j = 1; j <= m; j++ )
                a[i][j] *= -1;
    for ( int i = 1; i <= m; i++ )
        if ( scol[i] < 0 )
            for ( int j = 1; j <= n; j++ )
                a[j][i] *= -1;
    for ( int i = 1; i <= n; i++ )
        for ( int j = 1; j <= m; j++ )
            s += a[i][j];
    os << s;
    is.close();
    os.close();
    return 0;
}