#include<fstream>
#include<iostream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n,i,c,j;
bool v[2000001];
 int main(){
 	fin>>n;
 	c=0;
 	for(i=4;i<=n;i=i+2)
 		v[i]=1;
 	for(i=3;i*i<=n;i=i+2){
 		if(v[i]==0){
 			for(j=i*i;j<=n;j=j+i)
 				v[j]=1;
		 }
	}
 	for(i=1;i<=n;i=i+2)
 		if(v[i]==0)
 			c++;
 	fout<<c;
 	

 	return 0;
 }