using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;


class Magatro
{
    static int K = int.Parse(Console.ReadLine());
    static int cnt = 0;
    const int MAX = 2000000;
    static void Main()
    {
        Random rnd = new Random();
        for(int i = 0; i < MAX; i++)
        {
            int a = 0;
            int l = 0;
            while (a < K)
            {
                a += rnd.Next(1, 7);
                l++;
            }
            cnt += l;
        }
        Console.WriteLine((double)cnt / MAX);
    }

}