let () =
  Scanf.scanf "%d\n" @@ fun n ->
  let vrr = Array.init n @@ fun _ -> Scanf.scanf "%f " @@ fun d -> d in
  let _ = Array.fast_sort compare vrr in
  let lst = Array.to_list vrr in
  let ans = List.fold_left (fun ans x -> (ans +. x) /. 2.) (List.hd lst) (List.tl lst) in
  Printf.printf "%.1f\n" ans