#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");
int n , m ;
int main()
{
    f >> n >> m ;
    int a[n][m] ;
    for ( int i = 0 ; i < n ; i ++ )
        for ( int j = 0 ; j < m ; j ++ )
        f >> a[i][j] ;
        int k = 1 ;
    while ( k != 0 )
    {
        k = 0 ;
        for ( int i = 0 ; i < n ; i ++ )
        { int s = 0 ;
            for ( int j = 0 ; j < m ; j ++ )
            {
             s = s + a[i][j] ;
            }
            if ( s < 0 )
            { k ++ ;
               for ( int j = 0 ; j < m ; j ++ )
               {
                 a[i][j] = - a[i][j] ;
               }

            }
        }
        for ( int j = 0 ; j < m ; j ++ )
        { int s = 0 ;
            for ( int i = 0 ; i < m ; i ++ )
            {
             s = s + a[i][j] ;
            }
            if ( s < 0 )
            { k ++ ;
               for ( int i = 0 ; i < n ; i ++ )
               {
                 a[i][j] = - a[i][j] ;
               }

            }
        }
    }
    int s = 0 ;
    for ( int i = 0 ; i < n ; i ++ )
        for ( int j = 0 ; j < m ; j ++ )
        s = s + a[i][j] ;
        g << s ;
    return 0;
}