import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {
	
	public static long dfs(long[] memo, final int N, final int bit, final int K){
		if(memo[bit] >= 0){
			return memo[bit];
		}
		
		//System.out.println(Integer.toBinaryString(bit));
		
		final int all_bit_up = (1 << (K + 1)) - 1;
		if(all_bit_up == bit){ return memo[bit] = 0; }
		
		memo[bit] = 1;
		for(int k = K + 1; k < N; k++){
			if((bit & (1 << k)) != 0){ continue; }
			
			memo[bit] += dfs(memo, N, bit | (1 << k), k);
		}
		
		return memo[bit];
	}
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		final int K = sc.nextInt() - 1;
		
		long[] memo = new long[1 << N];
		Arrays.fill(memo, -1);
		
		System.out.println(dfs(memo, N, 1 << K, K));
	}

}