let solve n a_lst =
  if n mod 2 = 1 then
    List.nth a_lst (n / 2)
  else
    let a1 = List.nth a_lst (n / 2 - 1)
    and a2 = List.nth a_lst (n / 2) in
    (a1 +. a2) /. 2.

let () =
  let n = read_line () |> int_of_string
  and a_lst = read_line ()
              |> Str.split (Str.regexp_string " ")
              |> List.map float_of_string
              |> List.sort compare
  in
  solve n a_lst
  |> Printf.printf "%0.1f\n"