#include<stdio.h>
int main()
{ long a[16][16],i,j,m,n,s1,s2,s=0;
  FILE*f=fopen("flip.in","r");
  FILE*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",&a[i][j]);
  for (i=1;i<=n;i++)
   {  s1=0;
      s2=0;
      for (j=1;j<=m;j++)
	 if (a[i][j]>0) s1+=a[i][j];
	    else s2-=a[i][j];
      if (s2>s1)
	 for (j=1;j<=m;j++)
	   a[i][j]=-a[i][j]; }
 for (j=1;j<=m;j++)
   {  s1=0;
      s2=0;
      for (i=1;i<=n;i++)
	 if (a[i][j]>0) s1+=a[i][j];
	    else s2-=a[i][j];
      if (s2>s1)
	 for (i=1;i<=n;i++)
	   a[i][j]=-a[i][j]; }
 for (i=1;i<=n;i++)
   for (j=1;j<=m;j++)
      s+=a[i][j];
 fprintf(g,"%ld\n",s);
 return 0;}