4522001f ​

input = fill 3v (fill 3h black) |> rect ((#0 - 1, #1 - 1, #0, #1), green) |> rect ((2v, 2h, 2v, 2h), red)
output = fill 9v (fill 9h black) |> fold (λr. rect ((r.1 + 3 - 3 | r.1, r.2 + 3 - 3 | r.2, r.1 + 3, r.2 + 3), green)) #2
(VInt, HInt, UList (VInt, HInt))
(2v, 2h, {(1v, 1h), (5v, 5h)})
(3v, 3h, {(6v, 6h), (2v, 2h)})
(2v, 3h, ?)