#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in") ;
ofstream g("flip.out") ;
int n , m , a[20][20] , i , j , mi = 1000000  , s , h ;
int main()
{ f >> n >> m ;
int l[20] , k[20] ;
for ( i = 1 ; i <= n ; i ++ )
    for ( j = 1 ; j <= m ; j ++ )
        f >> a[i][j] ;
    for ( h = 1 ; h <= 20 ; h ++ )
    {
        l[h] = 0 ;
        k[h] = 0 ;
    }

    for ( i = 1 ; i <= n ; i ++ )
    {
        s = 0 ;
        for( j = 1 ; j <= m ; j ++ )
             s = s + a[i][j] ;
               if ( s < 0 )
               {
                l[i] = i  ;
                }
     }
  for ( j = 1 ; j <= m ; j ++ )
 {
     s = 0 ;
     for ( i = 1 ; i <= n ; i ++ )
      s = s + a[i][j] ;
      if ( s < 0 )
      {
          k[j] = j ;
      }
 }
    for ( h = 1 ; h <= n ; h ++ )
    {
        for ( i = l[h] ; i <= l[h] ; i ++ )
            for ( j = 1 ; j <= m ; j ++ )
                a[i][j] = - a[i][j] ;
    }
    for ( h = 1 ; h <= m ; h ++  )
        for ( j = k[h] ; j <= k[h] ; j ++ )
          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 = s + a[i][j] ;
     g << s ;
    return 0;
}