#yukicoder No.22 括弧の対応
N, K = map(int, input().split())
S = input()
d = []
cnt = 0
for i in range(N):
    if S[i] == "(":
        cnt += 1
    else:
        cnt -= 1
    d.append(cnt)

i = K - 1
if S[i] == ")":
    while True:
        i -= 1
        if d[i] == d[K - 1] + 1 and S[i] == "(":
            print(i + 1)
            break
else:
    while True:
        i += 1
        if d[i] == d[K - 1] - 1 and S[i] == ")":
            print(i + 1)
            break