using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var k = int.Parse(Console.ReadLine());
            var e = new double[k];
            e[0] = 1;
            for(var i = 1; i < k; i++)
            {
                e[i] = 1;
                for(var j = i - 1; j >= i - 6 && j >= 0; j--)
                {
                    e[i] += e[j] / 6;
                }
            }
            Console.WriteLine(e[k - 1]);
        }
    }
}