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

int main() {
  int a[] = {2, 3, 5, 7, 11, 13};
  int b[] = {4, 6, 8, 9, 10, 12};
  int k;
  cin >> k;
  int ans = 0;
  for (int i = 0; i < 6; i++) {
    for (int j = 0; j < 6; j++) {
      ans += (k == a[i] * b[j]);
    }
  }
  cout << fixed << setprecision(15) << (double)ans/36 << endl;
  return 0;
}