#include <iostream>
#include <string>

using namespace std;

long n,ans;

int main(){
	cin >> n;
	ans = 1;
	if(n == 1){
		cout << 0 << endl;
		return 0;
	}
	if(n == 2){
		cout << 1 << endl;
		return 0;
	}
	for(int i=3;i<=n;i=i+2){
		ans += 1;
		for(int j=3;j*j<=i;j=j+2){
			int k = i/j;
			if(i == k*j){
				ans -= 1;
				break;
			}
		}
	}
	
	cout << ans << endl;
	return 0;
}