#include <bits/stdc++.h>
#define sz size
#define pb push_back
#define er erase
#define in insert
#define fr first
#define sc second
#define mp make_pair
#define pi pair
#define _ ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
#define rc(s) return cout<<s,0
const int mod=1e9+7;
const int inf=1e5;
using namespace std;
std::set<int>::iterator it;
std::set<int>::iterator it1;

int n,rez;
char era[2000005];

signed main(){ _
    ifstream fin ("ciur.in");
    ofstream fout("ciur.out");
    cin >> n;
    for(int i=2;i<=n;i++){
        if(era[i]==NULL) rez++;
        for(int j=i+i;j<=n;j+=i){
            era[j]='1';
        }
    }
    cout<<rez;
}