using System;
class Program
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine();
            string[] arg = line.Split(' ');
            int[] numArgs = new int[arg.Length];
            for(int i = 0; i < numArgs.Length; ++i)
            {
                numArgs[i] = int.Parse(args[i]);
            }

            int pow = numArgs[0] >= numArgs[1] ? (int) Math.Pow(2, numArgs[0] - numArgs[1]) : 0;
            Console.WriteLine(pow);
        }
    }