func main()
	var n: int :: cui@inputInt()
	var k: int :: cui@inputInt()
	var ans: int :: 0
	if(k = 1)
		for i(1, n - 2)
			do ans :+ 2 ^ i - 1
		end for
	else
		do ans :: 2 ^ (n - k)
	end if
	do cui@print("\{ans}\n")
end func