#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <set>
#include <cstring>
#include <cmath>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i, k, n) for (int i = (int)(k); i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rREP(i, k, n) for (int i = (int)(n)-1; i >= k; i--)

#define debug(x) cerr<<#x<<": "<<x<<'\n'

#define fi first
#define se second

#define vi vector<int>
#define pb push_back
#define mp make_pair

#define pcnt __builtin_popcount

typedef long long ll;

const int inf = 100100100;
const int MOD = 998244353;
const double EPS = 1e-9;

bool s[1000000] = {};
int sosu[1000000] = {};
void erast(){
  memset(s,1,sizeof(s));
  s[1] = false;
  s[0] = false;
  REP(i,2,1000){
    if(s[i]){
      REP(j,2,1000000){
        if(i*j>=1000000) break;
        s[i*j] = false;
      }
    }
  }
  REP(i,2,1000000) sosu[i] = sosu[i-1]+s[i];
}

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    erast();
    int n;
    while(cin >> n){
      cout << sosu[n] << endl;
    }
    return 0;
}

