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

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


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