inpl = lambda: list(map(int,input().split()))
N, K = inpl()
S = input()
if S[K-1] == '(':
    i = K-1
else:
    i = 0
pool = [i]
for j in range(i+1,N):
    if S[j] == '(':
        pool.append(j)
    else:
        p = pool.pop()
        if j == K-1:
            print(p+1)
            break
        elif p == K-1:
            print(j+1)
            break