#include<iostream>
#include<vector>
#include<string>
using namespace std;

int main() {
	int a;
	while (cin >> a, a) {
		int sosuu = 0;
		if (a > 1)sosuu++;
		if (a > 2)sosuu++;
		for (int b = 5; b <= a; b+=2) {
			for (int c = 3;; c+=2) {
				if (b%c==0)break;
				if ((c + 1)*(c + 1) > b) { sosuu++;   break; }
			}
		}
		cout << sosuu << endl;
	}
}