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

int main()
{
	int n;
	vector<int> prime;

	while (cin >> n) {
		prime.push_back(2);

		for (int I = 2; I <= n; I++) {
			bool isPrime = true;
			for (int i = 0; i < prime.size(); i++) {
				if (I%prime[i] != 0)
					isPrime = false;
			}
			if (isPrime)
				prime.push_back(I);
		}
		cout << prime.size() << endl;
		prime.clear();
	}
	return 0;
}