def main():
    N, K = map(int, input().split())
    S = input()

    lst = [0] * N
    i = 0
    for j in range(N):
        if S[j] == '(':
            i += 1
            lst[j] = i
        else:
            lst[j] = i
            i -= 1

    i = lst[K-1]
    indexes = [j for j, x in enumerate(lst) if x == i]
    if indexes[0] == K - 1:
        print(indexes[1] + 1)
    else:
        print(indexes[0] + 1)

main()