N, K = map(int, input().split())
S = input()
list = []
count = 1
for i in S:
    if i == "(":
        list.append(count)
    if i == ")":
        L = list.pop()
        if L == K:
            print(count)
            break
        if count == K:
            print(L)
            break
    count = count + 1