#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
static const int MAX = 500005;
bool isPrime[MAX];

void makePrime() {
  for (int i = 0; i < MAX; i++)
    isPrime[i] = true;
  
  isPrime[0] = false;
  isPrime[1] = false;

  int n = sqrt(MAX);
  for (int i = 2; i <= n; i++) {
    if (!isPrime[i])
      continue;
    for (int j = i * 2; j < MAX; j += i)
      isPrime[j] = false;
  }
}

int main() {
  int N;
  cin >> N;
  vector<ll> p;
  makePrime();
  for (int i = 2; i <= N; i++) {
    if (isPrime[i])
      p.push_back(i);
  }
  int ans = 0;
  for (int i = 0; i < p.size(); i++) {
    for (int j = 0; j < p.size(); j++) {
      ll t = p[i] * p[i] - p[j];
      if (t < 1 || t > N)
        break;
      if (isPrime[t]) {
        ans++;
      }
    }
  }
  cout << ans << endl;
  return 0;
}