#include<iostream> 
#include<cmath> 
#include<cstdio> 
#include<algorithm> 
#include<cstring>
#include<string> 
using namespace std;
bool fun(int a){
	for(int i=2;i<a;i++){
		if(a%i == 0){
			return false; 
		}
	}
	return true;	
}
int main(){
	int n;
	cin >> n;
	bool b;
	int cnt=0;
	for(int i=2;i<=n;i++){
		b = fun(i);
		if(b){
			cnt++;
		}
	}
	cout << cnt;
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

bool cheakPrime(int number) {
    if (number <= 1) {
     	return false;
	} else {
	 	for (int i = 2; i < number; i++) {
	 	    if (number % i == 0) {
	 	 		return false;
			}
		}
		return true;
	}
}

int main() {
	int n;
	cin >> n;
	int counter = 0;
	for (int i = 2; i <=n; i++) {
		if (cheakPrime(i)) {
			counter = counter + 1;
			
		}
	}
	cout << counter;
	return 0;
}