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

int main() {
  int p[6] = { 2, 3, 5, 7, 11, 13 };
  int s[6] = { 4, 6, 8, 9, 10, 12 };
  int i, j, k;
  double count = 0;

  cin >> k;

  for (i = 0; i < 6; i++) {
    for (j = 0; j < 6; j++) {
      if (p[i] * s[j] == k) {
        count++;
      }
    }
  }

  cout << fixed << setprecision(13) << count / 36 << endl;

  return 0;
}