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

int main(){
  int dice1[6] = {2, 3, 5, 7, 11, 13};
  int dice2[6] = {4, 6, 8, 9, 10, 12};
  int k, count = 0;
  cin >> k;
  for(int i = 0; i < 6; i++){
    for(int j = 0; j < 6; j++){
      if(dice1[i] * dice2[j] == k)
        count++;
    }
  }
  cout.precision(15);
  cout << fixed << (double) count / 36 << endl;
}