#include<iostream>
#include<fstream>
#include<stdio.h>
#include<vector>
using namespace std;
vector<bool> v(3000000);
int main()
{int i,j,k,n;
ifstream fin("ciur.in");
  fin>>n;
  v[0]=v[1]=1;
  k=1;
  for(i=2;i<=n;i++)
    {if(v[i]==0)
    for(j=i;j*i<=n;j++)
       {v[j*i]=1;
       k++;}
    }
  freopen("ciur.out","w",stdout);
    printf("%d \n",n-k);


    return 0;
}