using System;
using System.Collections.Generic;

class ASCASC2
{
	static int N, K;
	static List<int> firstList = new List<int>();
	static List<int> latterList = new List<int>();

	static void Main(String[] args)
	{
		String[] vals = Console.ReadLine().Split(' ');
		N = int.Parse(vals[0]);
		K = int.Parse(vals[1]);
		firstList.Add(K);
		Console.WriteLine(CountOK(1));
	}

	static int CountOK(int i)
	{
		int ret = 0;
		if(i > N)
		{
			int firstMax = firstList[firstList.Count-1];
			if(latterList.Count == 0)
				return 0;
			int latterMin = latterList[0];
			if(firstMax > latterMin)
			{
				//DebugWrite();
				return 1;
			}
			else
				return 0;
		}
		if(i == K)
			return CountOK(i+1);

		if(i > K)
		{
			firstList.Add(i);
			ret+=CountOK(i+1);
			firstList.RemoveAt(firstList.Count-1);
		}
		latterList.Add(i);
		ret+=CountOK(i+1);
		latterList.RemoveAt(latterList.Count-1);

		return ret;
	}

	static void DebugWrite()
	{
		foreach(int v in firstList)
		{
			Console.Write("{0},",v);
		}
		Console.Write(" ");
		foreach(int v in latterList)
		{
			Console.Write("{0},",v);
		}
		Console.WriteLine();
	}
}