#include<fstream.h>
unsigned long a[10000];
int main()
{unsigned long n,i,p;

ifstream f("ciur.in");
ofstream g("ciur.out");
 f>>n;
  for(i=2;i<n;i++)
   {if(a[i]==0)
      {p=i;
       while(p<n)
	{p++;
	 if((p%i==0)&&(a[p]==0))
	   a[p]=1;}
    }}
    p=0;
   for(i=2;i<n;i++)
    if(a[i]==0) p++;
g<<p<<'\n';
f.close();
g.close();
return 0;
}