let stream_fold f init st =
  let result = ref init in
  Stream.iter (fun x -> result := f !result x) st;
  !result

let stream_to_rev_list st =
  stream_fold (fun result elem -> elem :: result) [] st



let () =
  Stream.from (fun i ->
    if i >= 3 then None
    else
      let c = (65 + i) |> char_of_int
      and h, w =
        read_line ()
        |> fun l -> Scanf.sscanf l "%d %d" (fun h w -> (h, w)) in
      Some(c, h, w))
  |> stream_to_rev_list
  |> List.sort (
    fun (_, h1, w1) (_, h2, w2) ->
	    let c = compare h2 h1 in
	    if c = 0 then compare w1 w2 else c)
  |> List.iter (fun (c, _, _) -> print_endline (String.make 1 c))