#include <fstream>
using namespace std;
ifstream f("filip.in");
ofstream g("filip.out");
long n,m,a[17][17];
void citire()
{f>>n>>m;
 int i,j;
 for(i=1;i<=n;i++)
  for(j=1;j<=m;j++)f>>a[i][j];
}
void trans_1(long a[17][17])
{int s,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]*=-1;
 }
}
void trans_2(long a[17][17])
{int i,j;
 long s;
 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]*=-1;
 }
}
void suma(long a[17][17])
{int i,j;
 long s=0;
 for(i=1;i<=n;i++)
  for(j=1;j<=m;j++)s+=a[i][j];
 g<<s;
}
int main()
{int i,j;
 citire();
 trans_1(a);
 trans_2(a);
 suma(a);
    return 0;
}