#include<stdio.h>
int main()
{
 long n,m,i,j,s,v[17][17];
 FILE *f,*g;
 f=fopen ("flip.in","r");
 g=fopen ("flip.out","w");
 fscanf(f,"%ld %ld",&n,&m);
 for(i=1;i<=n;i++)
		  for(j=1;j<=m;j++)fscanf(f,"%ld",&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];
 fprintf(g,"%ld\n",s);
 fclose(f);
 fclose(g);
 return 0;
 }