#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main() {
	int n;

	while(cin >> n) {
		int count = 0;

		for(int i = 2; i <= n; i++) {
			int yaku = 0;
			for(int j = 1; j <= i; j++) {
				if(i % j == 0) {
					yaku++;
				}
			}
			if(yaku == 2) {
				count++;
			}
		}

		cout << count << endl;
	}
}