let () = print_endline @@ Scanf.scanf "%d %d %d %d" @@ fun sx sy tx ty ->
  String.make (tx - sx) 'R' ^
  String.make (ty - sy) 'U' ^
  String.make (tx - sx) 'L' ^
  String.make (ty - sy) 'D' ^
  "D" ^
  String.make (tx - sx + 1) 'R' ^
  String.make (ty - sy + 1) 'U' ^
  "L" ^
  "U" ^
  String.make (tx - sx + 1) 'L' ^
  String.make (ty - sy + 1) 'D' ^
  "R"