package main

import "fmt"

func main() {
	var N, K uint
	fmt.Scan(&N, &K)
	count := 0
	for i := uint(1); i < 1 << N; i++ {
		mx1 := uint(0)
		mn1 := N
		mn2 := N
		for j := uint(0); j < N; j++ {
			if (1 << j & i) > 0 {
				mx1 = max(mx1, j + 1)
				mn1 = min(mn1, j + 1)
			} else {
				mn2 = min(mn2, j + 1)
			}
		}
		if mn1 == K && mx1 > mn2 {
			count++
		}
	}
	fmt.Println(count)
}

func max(a uint, b uint) uint {
	if a < b {
		return b
	}
	return a
}
func min(a uint, b uint) uint {
	if a < b {
		return a
	}
	return b
}