#include <fstream>
using namespace std;

int main() {
	ifstream fin("ciur.in");
	ofstream fout("ciur.out");
	int n;
	fin >> n;
	int cnt_non_prime_numbers = 0;
	for (int i = 3; i * i <= n; i += 2) {
		int k = 3;
		while (i * k <= n) {
			cnt_non_prime_numbers++;
			k += 2;
		}
	}
	int copy_n = n;
	if (n % 2) {
		--copy_n;
	}
	cnt_non_prime_numbers = cnt_non_prime_numbers + copy_n / 2 - 1;
	fout << n - 1 - cnt_non_prime_numbers;
	return 0;
}