#include <bits/stdc++.h>
using i64 = long long;

int main() {
  int n;
  std::cin >> n;
  std::vector<int> ps;
  std::vector<int> comp(n + 1);
  for (int i = 2; i <= n; i++) {
    if (!comp[i]) ps.push_back(i);
    for (int j = 0; j < ps.size() && i * ps[j] <= n; j++) {
      comp[i * ps[j]] = 1;
      if (i % ps[j] == 0) break;
    }
  }

  int ret = 0;
  for (auto p : ps) {
    auto t = p * p - 2;
    if (p > n || t > n) break;
    auto it = std::lower_bound(ps.begin(), ps.end(), t);
    if (it != ps.end() && *it == t) {
      if (t == p) ret++;
      else ret += 2;
    }
  }

  std::cout << ret << std::endl;

  return 0;
}