open System

// val read_line : unit -> int option
let read_line () =
  let input =
    Console.ReadLine ()
  in
    match Int32.TryParse input with
    | (false, _) ->
      None

    | (true, x) ->
      Some x


// val get_set_from_prompt : string -> int set
let get_set_from_prompt prompt =
  printfn "%s" prompt

  let rec loop xs =
    match read_line () with
    | None ->
      xs

    | Some x ->
      loop ( x :: xs )

  set <| loop []


[<EntryPoint>]
let main argv =
  let set1 =
    get_set_from_prompt "input numbers for set 1:"

  let set2 =
    get_set_from_prompt "input numbers for set 2:"

  let output =
    Set.union set1 set2

  printfn "output numbers (union of set 1 and set 2):"
  printfn "%A" output
  0 // return an integer exit code