#include <iostream>
	
#include <fstream>
	
using namespace std;
	
 
	
int Ciur(int number){
	
	int vector[1000000];
	
	int nr = 1;
	
	for (int i = 3; i <= number; i = i + 2){
	
		if(vector[i] == 0){
	
			nr++;
	
		}
	
		for(int j = i + i + i; j <= number; j = j + i + i){
	
			vector[j] = 1;
	
		}
	
	}
	
	return nr;
	
}
	
 
	
int main(){
	
	ifstream fin("ciur.in");
	
	ofstream fout("ciur.out");
	
    int n, rez;
	
	fin >> n;
	
	rez = Ciur(n);
	
	fout << rez << '\n';
	
	return 0;
	
}