n, k = map(int, input().split())
k = k - 1
ss = list(input())

left_start = True if ss[k] == "(" else False
ss_slice = []

if left_start:
    ss_slice = ss[k:]
else:
    ss_slice = list(reversed(ss[:k+1]))

left, right = 0, 0

for i, s in enumerate(ss_slice):

    if s == "(":
        left += 1
    else:
        right +=1

    if left == right:
        if left_start:
            print(k + i + 1)
        else:
            print(k - i + 1)
        break