using System;
using System.Linq;
using System.Collections.Generic;

public class Test
{
	public static void Main()
	{
		var x = Console.ReadLine()
				.Split(' ')
				.Select(n => int.Parse(n))
				.ToList();
		
		if (x[1] == 1) Console.WriteLine(Math.Pow(2, x[0] -x[1]) - x[0]);
		else Console.WriteLine(Math.Pow(2, x[0] -x[1]));
	}
}