#include<stdio.h>
long long n,prim[2000001],nr;
int primes(long long n)
{
 int i,j,nr=1;
 for(i=2;i<=n;++i) prim[i]=1;
 for(i=4;i<=n;i+=2) {prim[i]=0; nr++;}
 for(i=3; i*i<=n; i+=2)
	if(prim[i])
		for(j=i*i;j<=n;j+=i) {prim[j]=0; nr++;}
 return n-nr;
}
int main()
{
 freopen("ciur.in","rt",stdin);
 freopen("ciur.out","wt",stdout);
 scanf("%lld",&n);
 nr=primes(n);
 printf("%lld",nr);
 return 0;
}