#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <cstring>
#include <fstream>
#include <algorithm>
#include <set>
#include <bitset>
#include <cmath>
#include <map>
#include <vector>
#include <queue>
#include <stack>
#define INF 1e9
#include <bits/stdc++.h>
using namespace std;
bitset<2000000> p;
int main()
{
   int n;
   cin>>n;
   p[0] =1;
   p[1] = 1;
   for(int i=2;i<=sqrt(n);i++)
   {
       if(p[i] == 0)
       for(int j=2;j<=n/i;j++)
        p[i*j] = 1;
   }
    int contor =0 ;
    for(int i=1;i<=n;i++)
        if(p[i]==0)contor++;
    cout<<contor;
  return 0;
}