#include <iostream>
#include <cmath>
using namespace std;
void cprime(int, int&);

int main() {
	int n;
	
	while (cin >> n) {
		int count = 0;
		for (int i = 0; i < n;i++) {
			cprime(i + 1,count);
		}
		cout << count << endl;
	}
}

void cprime(int n, int& count) {
	if (n == 1) return;
	for (int i = 2; i <= sqrt(n);i++) {
		if (n % i == 0) return;
	}
	count++;

	return;
}