N, K = list(map(int, input().split()))
S = input()

result = 0
k = K - 1

if S[k] == '(':
	nesing = 0
	for i in range(k, N):
		if S[i] == '(':
			nesting += 1
		else:
			nesting -= 1
			if nesting == 0:
				result = i + 1
				break
else:
	nesting = 0
	for i in range(k, -1, -1):
		if S[i] == '(':
			nesting -= 1
			if nesting == 0:
				result = i + 1
				break
		else:
			nesting += 1


print(result)