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(), K = reader.Int();
        float[] A = DP(N, K);
        float[] B = DP(N, 0);
        for (int i = 1; i < B.Length; i++)
            B[i] += B[i - 1];
        float ans = 0;
        for (int i = 1; i < A.Length; i++)
            ans += A[i] * B[i - 1];

        Console.WriteLine(ans);
    }

    float[] DP(int N, int K)
    {
        float[] dp = new float[(int)Math.Pow(6, N) + 5];
        float[] next = new float[dp.Length];
        float mult = 1.0f / 6;
        int[] dice1 = { 4, 4, 5, 5, 6, 6 };
        int[] dice2 = { 1, 2, 3, 4, 5, 6 };
        dp[0] = 1;

        for (int i = 0; i < N; i++)
        {
            if (i == K) Swap(ref dice1, ref dice2);
            Array.Clear(next, 0, next.Length);
            for (int sum = 0; sum <= i * 6; sum++)
                foreach (int d in dice1)
                    next[sum + d] += dp[sum] * mult;
            Swap(ref dp, ref next);
        }

        return dp;
    }

    void Swap<T>(ref T a, ref T b) { T t = a; a = b; b = t; }




    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++]; }
    }
}