let solve k s =
  let int_of_p = function | '(' -> 1 | _ -> -1 in
  let dir = int_of_p s.[k - 1] in
  let rec solve' i dsum =
    let ci = s.[i] in
    let dsum = dsum + (int_of_p ci) in
    if dsum = 0 then
      i + 1
    else
      solve' (i + dir) dsum
  in
  solve' (k - 1 + dir) dir

let () =
  let k = read_line ()
          |> fun l -> Scanf.sscanf l "%d %d" (fun _ k -> k)
  and s = read_line () in
  solve k s
  |> string_of_int
  |> print_endline