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

constexpr int NMAX = 1e7;
int primes[665000], np = 0;
int8_t mu[NMAX + 1];

int main() {
	int N;
	cin >> N;
	
	memset(mu, 2, sizeof(mu));
	mu[0] = 0, mu[1] = 1;
	
	int ans = 1;
	for(int i = 2; i <= N; ++i) {
		if(mu[i] == 2) {
			primes[np++] = i;
			mu[i] = -1;
		}
		const int8_t muval = -mu[i];
		for(int j = 0; j < np; ++j) {
			const int p = primes[j];
			const int idx = i * p;
			if(idx > N) break;
			
			if(i % p == 0) {
				mu[idx] = 0;
				break;
			} else {
				mu[idx] = muval;
			}
		}
		
		ans += mu[i];
	}
	
	cout << ans << "\n";
}