N, K = list(map(int, input().split()))
S = input()
c = 0
if S[K - 1] == "(":
    for i in range(K, N):
        if S[i] == "(":
            c += 1
        else:
            if c != 0:
                c -= 1
            else:
                print(i + 1)
                break
else:
    for i in range(K - 2, -1, -1):
        if S[i] == ")":
            c += 1
        else:
            if c != 0:
                c -= 1
            else:
                print(i + 1)
                break