#include <iostream>
#include <cmath>
using namespace std;
bool isprime(int x) {
	if (x <= 1) return false;
	for (int i = 2; i < x; ++i) {
		if(x % i == 0) {
			return false;
		} else continue;
	}
	return true;
}
int main() {
	long long n;
	long long cnt = 0;
	cin >> n;
	for (int i = 1; i <= n; ++i) {
		if (isprime(i)) { 
		    //cout << i << endl;
			cnt++;
		}
	}
	cout << cnt << endl;
	return 0;
}