N,K = map(int,raw_input().split())
S = raw_input()
if S[K-1] == "(":
	tmp = 1
	seq = range(K,N)
else:
	tmp = -1
	seq = range(K-2,-1,-1)
for i in seq:
	tmp += 1 if (S[i] == "(") else -1
	if tmp == 0:
		break
print i+1