
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <cmath>
#define pi 3.14159265358979323846264338
using namespace std;

int main() {
	int n;
	while (cin >> n) {
		vector<int> sos;
		sos.emplace_back(2);
		int s = 1;
		for (int j = 2; j <= n; j++) {
			for (int i = 0; i < sos.size(); i++) {
				if (j%sos[i] == 0) {
					break;
				}
				if (sos[i]>sqrt(j)) {
					sos.emplace_back(j);
					s++;
					break;
				}
			}
		}
		cout << s << endl;
	}
	return 0;
}