using System;
using System.Collections;
using System.Collections.Generic;
 
class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		double[][] P=new double[2][];
		P[0]=new double[121];
		P[0][60]=1.0;
		
		Dictionary<int,int> dk=new Dictionary<int,int>();
		for(int i=1;i<=6;i++){
			for(int j=4;j<=6;j++){
				int diff=j-i;
				if(!dk.ContainsKey(diff))dk.Add(diff,0);
				dk[diff]++;
				dk[diff]++;
			}
		}
		Dictionary<int,int> dn=new Dictionary<int,int>();
		for(int i=1;i<=6;i++){
			for(int j=1;j<=6;j++){
				int diff=j-i;
				if(!dn.ContainsKey(diff))dn.Add(diff,0);
				dn[diff]++;
			}
		}
		int now=0;
		int next=0;
		
		
		for(int i=0;i<N;i++){
			now=i%2;
			next=1-now;
			P[next]=new double[121];
			if(i<K){
				for(int j=0;j<121;j++){
					if(P[now][j]!=0){
						foreach(int k in dk.Keys){
							P[next][j+k]+=P[now][j]/36.0*dk[k];
						}
					}
				}
			}else{
				for(int j=0;j<121;j++){
					if(P[now][j]!=0){
						foreach(int k in dn.Keys){
							P[next][j+k]+=P[now][j]/36.0*dn[k];
						}
					}
				}
			}
		}
		
		double ans=0;
		for(int j=60+1;j<121;j++){
			ans+=P[next][j];
		}
		Console.WriteLine(ans);
		
	}
	int N;
	int K;
	public Sol(){
		N=ri();
		K=ri();
	}




	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(){return Console.ReadLine().Split(' ');}
	static int[] ria(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>int.Parse(e));}
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
	static double[] rda(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>double.Parse(e));}
}