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

if S[K - 1] == '(':
    tmp = 1
    for i in range(K, N):
        tmp += 1 if S[i] == '(' else -1
        if not tmp:
            print(i + 1)
            break

else:
    tmp = -1
    for i in range(K - 2, -1, -1):
        tmp += 1 if S[i] == '(' else -1
        if not tmp:
            print(i + 1)
            break