/*
TASK:necklace
LANG:C++
*/
#include<iostream.h>
#include<math.h>
int main()
{ long x,y,n,i,p,q,br=0,d;
  cin>>n;
  x=1;
  for(i=3;i<=n;i++) if (i%2!=0) x++;
  if (x%3==0) br++;
  y=1;
  for(i=2;i<=n;i++) if (i%2==0) y++;
  if (y%3==0) br++;
  for(p=1;p<=x;p++)
   for(q=1;q<=y-1;q++)
   { if(p+q==n) { d=abs(p-q);if (d%3==0) br++;}

	  d=abs(p-q);
	   if (d%3==0) br++;

   }
  cout<<br<<endl;
return 0;
}