#include <bits/stdc++.h>
#define dim 1000005
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bitset<dim> fr;
int n,i,nr,j;
int main(){
   fin>>n;
   /// de la 2*i+1 adica 3 adaug cate 2
   /// vorbim despre 3(2*i+1)
   /// 6i + 3
   /// 2*(3i+1) + 1
   /// adaug 2(2*i+1) la j
   ///
    if(n==2){
        cout<<1;
        return 0;
    }
    if(n%2==0)
        n--;
    n/=2;
   for(i=1;i<=n;i++){
    if(fr[i]==0){
        nr++;
        for(j=3*i+1;j<=n;j+=2*i+1){
            fr[j]=1;
        }
    }
   }
   fout<<nr+1;
}