#include <iostream>
#include <fstream>
#define Nmax 17
using namespace std;
int a[Nmax][Nmax] ;
int n , m ;
ifstream f("flip.in") ;
ofstream g("flip.out") ;
void com_lin(int b)
{
    for ( int j = 1 ; j <= m ; j ++ )
        a[b][j] = -a[b][j] ;
}
void com_col(int b)
{
    for ( int i = 1 ; i <= n ; i ++ )
        a[i][b] = - a[i][b] ;
}
int b = 0 , mins = 0  ;
int main()
{
    f >> n >> m ;
    for ( int i = 1 ; i <= n ; i ++ )
        for ( int j = 1 ; j <= m ; j ++ )
        f >> a[i][j] ;

     for ( int i = 1 ; i <= n ; i ++ )
        {  int s = 0 ;
         for ( int j = 1 ; j <= m ; j ++ )
          s = s + a[i][j] ;
         if ( s < 0  )
         {
             com_lin(i) ;
         }
        }
        for ( int j = 1 ; j <= m ; j ++ )
        { int s = 0 ;
            for ( int i = 1 ; i <= n ; i ++ )
                s = s + a[i][j] ;
            if ( s < 0 )
                com_col(j) ;
        }
      int sm = 0 ;
      for ( int i = 1 ; i <= n ; i ++ )
        for ( int j = 1 ; j <= m ; j ++ )
          sm = sm + a[i][j] ;
          g << sm ;

    return 0;
}