n, k = map(int, input().split(" "))
k -= 1
b = input()
s = [i for i in range(n)]
while True:
	i = b.index("()")
	p = [s.pop(i), s.pop(i)]
	b = b.replace("()", "", 1)
	if k in p:
		print(sum(p) - k + 1)
		break