N, K = map(int, input().split())
S = input()
lcount = 0
rcount = 0
judge = 0

if S[K-1] == '(':
    for i in range(K):
        if S[i] == '(':
            lcount += 1
        else:
            lcount -= 1
    judge = lcount - 1

    i += 1
    while lcount != judge :
        if i >= N:
            break
        if S[i] == ')':
            lcount -= 1
        else:
            lcount += 1
        i += 1
    print(i)

else:
    for i in range(N-1, K-2, -1):
        if S[i] == ')':
            rcount += 1
        else:
            rcount -= 1

    judge = rcount - 1
    i -= 1

    while rcount != judge :
        if i < 0 :
            break
        if S[i] == '(':
            rcount -= 1
        else:
            rcount += 1
        i -= 1

    print(i+2)