(* abc138 b problem *)
open Scanf;;
open List;;

let rec list_init n f =
  if n <= 0 then []
  else let x = f () in x :: list_init (n-1) f;;

let () = Scanf.scanf "%d"
           (fun n -> list_init n (fun _ -> Scanf.scanf " %f" (fun v -> v)))
         |> stable_sort Pervasives.compare
         |> (fun arr -> fold_left (fun x y -> (x +. y) /. 2.0) (hd arr) arr)
         |> print_float
         |> print_newline;;

exit 0;;