# -*- coding:utf-8 -*-

if __name__ == "__main__":
	n,k = map(int,raw_input().split())
	s = raw_input()
	i = 1
	if s[k-1] == "(":
		while i > 0:
			k += 1
			if s[k-1] == "(":
				i += 1
			else:
				i -= 1
	else:
		while i > 0:
			k -= 1
			if s[k-1] == ")":
				i += 1
			else:
				i -= 1
	print k