#include <iostream>
#include <iomanip>
using namespace std;

int main() {
  int a[] = { 2, 3, 5, 7, 11, 13 };
  int b[] = { 4, 6, 8, 9, 10, 12 };
  int k, cnt = 0;
  cin >> k;
  for (int i = 0; i < 6; i++) {
    for (int j = 0; j < 6; j++) {
      if (a[i] * b[j] == k) cnt++;
    }
  }
  cout << fixed << setprecision(14) << cnt / 36.0 << endl;
}