#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define vl vector<ll>
auto _ = []() { ios::sync_with_stdio(false); cin.tie(nullptr); return 0; }();

int main() {
  
  ll N; cin >> N;
  vl mu(N + 1, 1);
  
  vector<bool> prime(N + 1, true);
  
  for (ll i = 2; i <= N; i++) {
    
    if (prime[i]) {
      
      for (ll j = i; j <= N; j += i) {
        
        prime[j] = false;
        
        mu[j] *= -1;
        
      }
      
      for (ll j = i * i; j <= N; j += i * i) mu[j] = 0;
      
    }
    
  }
  
  ll ans = 0;
  
  for (ll k = 1; k <= N; k++) ans += mu[k];
  
  cout << ans << "\n";
  
  return 0;
  
}