N, K = map(int, input().split())
S = list(input())
stack = []
ans = [-1] * N
for i in range(N):
	if S[i] == "(":
		stack.append(("(", i))
	else:
		now = stack.pop()[1]
		ans[now] = i
		ans[i] = now
print(ans[K - 1] + 1)