//
//  main.cpp
//  C++ - teste
//
//  Created by Filip Cuciuc on 03/02/2020.
//  Copyright © 2020 Filip Cuciuc. All rights reserved.
//

//#include <iostream>
#include <stdio.h>
#include <fstream>
#include <algorithm>
#include <vector>
#include <queue>
#include <math.h>
#include <map>
//#include "MED.h"
using namespace std;
//using namespace std::chrono;

ifstream cin("ciur.in");
ofstream cout("ciur.out");

const int MAX = 2e6 + 5;
int n, used[MAX];
int ans;

int main() {
   // auto start = high_resolution_clock::now();
    cin >> n;
    for (int i = 2; i <= n; i++) {
        if (used[i]) {
            continue;
        }
        int var = i;
        
        for (int j = 2; j <= n / i; j++) {
            if(var * j <= n)
                used[var * j] = 1;
        }
        
        ans++;
    }
    
    cout << ans;
    
//    auto stop = high_resolution_clock::now();
//    auto duration = duration_cast<microseconds>(stop - start);
//    cout << "Time taken by function: "
//    << duration.count() << " microseconds" << endl;
   
      
   return 0;
}