#include<fstream.h>
int main()
{
 int n,m,i,j,s,v[16][16];
 ifstream f("flip.in");
 ofstream g("flip.out");
 f>>n>>m;
 for(i=1;i<=n;i++)
		  for(j=1;j<=m;j++)f>>v[i][j];
 for(i=1;i<=n;i++){
		   s=0;
		   for(j=1;j<=m;j++)s+=v[i][j];
		   if(s<=0)for(j=1;j<=m;j++)v[i][j]*=-1;
		   }
 for(j=1;j<=m;j++){
		   s=0;
		   for(i=1;i<=n;i++)s+=v[i][j];
		   if(s<=0)for(i=1;i<=n;i++)v[i][j]*=-1;
		   }
 s=0;
 for(i=1;i<=n;i++)for(j=1;j<=m;j++)s+=v[i][j];
 g<<s;
 g.close();
 f.close();
 return 0;
 }