Scanf.scanf "%d" (fun n ->
    let a = Array.init n (fun _ -> Scanf.scanf " %d" (fun a -> a)) in
    Array.sort compare a;
    Printf.printf "%.1f\n" @@
        if n mod 2 = 1 then float a.(n / 2) else float (a.(n / 2) + a.(n / 2 - 1)) /. 2.
)