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

using ll = long long int;

vector<int> eratosthenes(int n) {
  vector<bool> prime(n+1, true);
  vector<int> p;
  prime[0] = false;
  prime[1] = false;
  for (int i = 2; i <= n; i++) {
    if (!prime[i])
      continue;
    p.push_back(i);
    for (int j = i*2; j <= n; j += i)
      prime[j] = false;
  }
  return p;
}

int main() {
  ll N;
  cin >> N;
  vector<int> p = eratosthenes(60);
  ll po = 1;
  int n = 0;
  while (po * p[n] < N && n < 15) {
    po *= p[n];
    n++;
  }
  cout << n << endl;
  return 0;
}