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

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