import sequtils, strutils, algorithm

var
    n,k, e:int
    nk = readLine(stdin).split.map(parseInt)
    s = readLine(stdin)
    rev:bool

(n,k) = nk
if k > int(len(s) / 2):
    reverse(s)
    k = s.len - k + 1
    rev = true

proc main():int =
    for i in (k - 1)..<s.len:
        if s[i] == '(':
            e += 1
        elif s[i] == ')':
            e -= 1
        if e == 0:
            return i

if rev == true: echo len(s) - main()
else: echo main() + 1