N, K = map(int, input().split())
S = input()
count = 1
ck = 0

if S[K - 1] == "(":
    for i in range(K,N + 1):
        if S[i] == "(":
            count += 1
        else:
            count -= 1
        if count == 0:
            print(i + 1)
            break


if S[K - 1] == ")":
    for i in range(N - K + 2, N + 1):
        if S[-i] == ")":
            count += 1
        else:
            count -= 1
        if count == 0:
            print(N - i + 1)
            break