#include<fstream>
using namespace std;
ifstream fi("ciur.in");
ofstream fo("ciur.out");
long int v[10000000],k=0;
int main(){
	int n;
	fi>>n;
	for(int i=3;i<=n;i+=2)
	    v[i]=1;
	    for(int i=2;i<=n;i++)
	      if(v[i])
{
	      k++;
	      for(int j=2*i;j<=n;j+=i)
	         v[j]=0;
	}	
	fo<<k+1<<" ";
	fi.close();
	fo.close();
	return 0;
}