JaeHyeonKim19

import java.io.*;
import java.util.*;

public class Main {
	static int count = 0;
	static int [] seats;
	static boolean [] isReserved;

	static void rec(int waiting, int index) {
		if(waiting == 0) {
			count++;
			return;
		}
		for(int i = index + 2; i <= seats.length - (waiting * 2 - 1); i++) {
			rec(waiting - 1, i);
		}
	}

	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		int k = Integer.parseInt(st.nextToken());
		seats = new int [n];
		isReserved = new boolean[n];
		for(int i = 0; i <= n - (k * 2 - 1); i++) {
			rec(k - 1, i);
		}
		System.out.print(count);
	}
}