let () = Scanf.scanf "%d" @@ fun n ->
  let aa = Array.init n @@ fun _ -> Scanf.scanf " %f" Fun.id in
  let () = Array.sort compare aa in
  let ans = ref aa.(0) in
  for i = 1 to n - 1 do
    ans := (!ans +. aa.(i)) /. 2.0
  done;
  Printf.printf "%f\n" !ans
  