Scanf.scanf "%d" (fun n ->
    let a = Array.init n (fun _ -> Scanf.scanf " %d" (fun a -> a)) in

    let rec loop_i i acc =
        let rec loop_j j acc =
            if j >= n then acc else loop_j (j + 1) (max acc (a.(i) lxor a.(j)))
        in
        if i = n then acc else loop_i (i + 1) (loop_j (i + 1) acc)
    in
    loop_i 0 0 |> Printf.printf "%d\n"
)