#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");

///2 il iei separat, ct=1
///sari nr pare (de aceea afisam din 2 in 2, bitset-memorie putina)

int main()
{
  bitset <1000000> v;
  int n,ct=1,i;
  fin>>n;
for(i=3;i*i<=n;i+=2)
{
    if(v[i]==false)
    {
        ct++;
    for(int j=i*i;j<=n;j+=2*i)
    {
        v[j]=true;
    }
    }
}
for(;i<=n;i+=2)
{
    if(v[i]==false)
        ct++;
}
fout<<ct;

}