n, k = [int(x) for x in input().split()]
s = input()

if s[k - 1] == '(':
    cnt = 0
    for i, c in enumerate(s[k - 1:]):
        if c == '(':
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0:
            res = k + i
            break
else:
    cnt = 0
    for i, c in enumerate(reversed(s[:k])):
        if c == ')':
            cnt += 1
        else:
            cnt -= 1
        if cnt == 0:
            res = k - i
            break

print(res)