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

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