# yukicoder No.22 括弧の対応

N, K = map(int, input().split())
S = input()
c = 0

if S[K - 1] == "(":
    for (i, s) in enumerate(S[K:]):
        if s == "(":
            c += 1
        else:
            if c == 0:
                print(K + i + 1)
                break
            else:
                c -= 1
else:
    for (i, s) in enumerate(S[:K - 1][::-1]):
        if s == ")":
            c += 1
        else:
            if c == 0:
                print(K - i - 1)
                break
            else:
                c -= 1