import java.util.*;
import java.lang.*;
import java.io.*;
 
class Ideone
{
	public static void main (String[] args) 
	{
		int n; //описание переменных
	    double x;
	    Scanner sc = new Scanner(System.in);
	    n = sc.nextInt(); //ввод условий
	    x = sc.nextDouble();
	    double sum=0;
	    double degree=1;
	    for(int i=1;i<=n;i++)
	    {
	        degree=degree*2; //вычисление степеней 2
	        sum=sum+(x+Math.cos(i*x))/degree; //вычисление суммы
	    }
	    System.out.printf("%4.2f\n",sum);
	}
}

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NSAy

5 2