#include"stdio.h"
#include<bitset>
using namespace std;
bitset<2000000> pr;

long n,q=0;

void genprime(long n)
{ 	 
	 pr.reset();
 	 for(long g=2;g<=n;g++)
 	 if(!pr[g])for(long h=g*2;h<=n;h+=g)pr[h]=1;
     q=n-(long)(pr.count())-1;}

int main()
{freopen("ciur.in","r",stdin);freopen("ciur.out","w",stdout);
scanf("%ld",&n);genprime(n);printf("%ld\n",q);
return 0;}