#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin>>n;
  vector<long> primes;
  bool checked[n+1];
  for (int i=0; i<=n; i++) checked[i] = false;
  for (int i=2; i<=n; i++) {
    if (checked[i]) {
      continue;
    }
    primes.push_back(i);
    for (int j=2*i; j<=n; j+=i) {
      checked[j] = true;
    }
  }
  int cnt = 0;
  for (long r: primes) {
    long q = r * r - 2;
    auto it = lower_bound(primes.begin(), primes.end(), q);
    if (it == primes.end()) {
      continue;
    }
    if (*it == q) {
      if (q == r) {
        ++cnt;
      } else {
        cnt += 2;
      }
    }
  }
  cout<<cnt<<endl;
}