#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<int, int> PII;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define MP make_pair
#define PB push_back
#define MOD 1000000007
#define INF (1LL << 30)
#define LLINF (1LL << 60)
#define PI 3.14159265359
#define EPS 1e-12
#define int ll

int prime[1000000];
signed main(void) {
  REP(i, 1000000) prime[i] = 1;
  prime[0] = prime[1] = 0;
  for (int i = 2; i * i <= 1000000; i++) {
  	if (prime[i]) {
  		for (int j = 2 * i; j <= 1000000; j += i) {
  			prime[j] = 0;
  		}
  	}
  }
  //REP(i, 10) cout << prime[i] << " "; cout << endl;
  FOR(i, 1, 1000000) {
    prime[i] += prime[i-1];
    //cout << prime[i] << endl;
  }
  int n;
  while (cin >> n) {
    cout << prime[n] << endl;
  }
  return 0;
}