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
		; = 2^1 + 2^2 + ... + 2^(n-2) - (n - 2)
		; = 2^(n-1) - n
		do ans :: 2 ^ (n - 1) - n
	else
		do ans :: 2 ^ (n - k)
	end if
	do cui@print("\{ans}\n")
end func