using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;

class Magatro
{

    static void Main()
    {
        int N, K;
        string[] s = Console.ReadLine().Split(' ');
        N = int.Parse(s[0]);
        K = int.Parse(s[1]);
        if (K == 1)
        {
            Console.WriteLine(Math.Pow(2,--N)-N);
            return;
        }
        Console.WriteLine(Math.Pow(2, N - K));
    }
}