#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
const int N = 2000010;
bitset<N> v;
int n,i,ct,j,a;
int main()
{
    fin>>n;
    v[1]=1;
    for(i=2;i*i<n;i++)
        if(v[i]==0)
        for(j=i*i;j<=n;j=j+i)
        v[j]=1;
    ct=n-v.count();
    fout<<ct;
    return 0;
}