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

count = [1] * N

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

print(index)