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[] E=new double[K+10];
		for(int k=K+10-1;k>=0;k--){
			if(k>=K){
				E[k]=0.0;
				continue;
			}
			E[k]=E[k+1]/6.0+E[k+2]/6.0+E[k+3]/6.0+E[k+4]/6.0+E[k+5]/6.0+E[k+6]/6.0+1.0;
		}
		Console.WriteLine(E[0]);
	}
	int K;
	public Sol(){
		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));}
}