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

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