N, K = map(int, input().split())
S = str(input())
i = K
j = 1

if S[K] == '(':
	while i <= N-1:
		if S[i] == '(':
			j += 1
		else:
			j -= 1
			
		i += 1
		if j == 0:
			print(i)
			break

else:
	while i >= 0:
		if S[i] == ')':
			j += 1
		else:
			j -= 1
			
		i -= 1
		if j == 0:
			print(i)
			break