using System;
using System.IO;
using System.Text;
using System.Linq;
using System.Diagnostics;
using System.Collections.Generic;
using Enu = System.Linq.Enumerable;

class Program
{
    void Solve()
    {
        int N = reader.Int();
        var mat = Enu.Range(0, N).Select(i => new double[N + 1]).ToArray();
        for (int r = 0; r < N; r++)
        {
            mat[r][r] = mat[r][N] = 6;
            for (int d = 1; d <= 6; d++)
            {
                int c = (r + d > N) ? 0 : r + d;
                if (c < N) mat[r][c]--;
            }
        }
        GaussJordan(mat);
        Console.WriteLine(mat[0][N]);
    }

    static bool GaussJordan(double[][] M)
    {
        double EPS = 1e-10;
        int R = M.Length;
        int C = M[0].Length;

        for (int i = 0; i < R; i++)
        {
            int pivot = i;
            for (int k = i + 1; k < R; k++)
                if (Math.Abs(M[k][i]) > Math.Abs(M[pivot][i]))
                    pivot = k;
            var t = M[pivot]; M[pivot] = M[i]; M[i] = t;
            if (Math.Abs(M[i][i]) < EPS) return false;
            for (int j = C - 1; j >= i; j--)
                M[i][j] /= M[i][i];
            for (int k = 0; k < R; k++)
                if (k != i)
                    for (int j = C - 1; j >= i; j--)
                        M[k][j] -= M[k][i] * M[i][j];
        }
        return true;
    }



    static void Main() { new Program().Solve(); }
    Reader reader = new Reader(Console.In);
    class Reader
    {
        private readonly TextReader reader;
        private readonly char[] separator = { ' ' };
        private readonly StringSplitOptions removeOp = StringSplitOptions.RemoveEmptyEntries;
        private string[] A = new string[0];
        private int i;

        public Reader(TextReader r) { reader = r; }
        public bool HasNext() { return Enqueue(); }
        public string String() { return Dequeue(); }
        public int Int() { return int.Parse(Dequeue()); }
        public long Long() { return long.Parse(Dequeue()); }
        public double Double() { return double.Parse(Dequeue()); }
        public int[] IntLine() { var s = Line(); return s == "" ? new int[0] : Array.ConvertAll(Split(s), int.Parse); }
        public int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
        public int[][] IntGrid(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
        public string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
        public string Line() { return reader.ReadLine().Trim(); }
        private string[] Split(string s) { return s.Split(separator, removeOp); }
        private bool Enqueue()
        {
            if (i < A.Length) return true;
            string line = reader.ReadLine();
            if (line == null) return false;
            if (line == "") return Enqueue();
            A = Split(line);
            i = 0;
            return true;
        }
        private string Dequeue() { Enqueue(); return A[i++]; }
    }
}