ce9e57f2 ​

input = fill #0 (fill 9h black) |> fold (λr. rect ((r.1, r.2, #0, r.2), red)) #1
output = fill #0 (fill 9h black) |> fold (λr. rect ((r.1, r.2, #0, r.2), teal)) #2 |> fold (λr. rect ((r.1, r.2, r.3, r.2), red)) #3
(VInt, UList (VInt, HInt), UList (VInt, HInt), UList (VInt, HInt, VInt))
(7v, {(5v, 8h), (4v, 6h), (3v, 4h), (2v, 2h)}, {(7v, 8h), (6v, 6h), (6v, 4h), (5v, 2h)}, {(5v, 8h, 6v), (4v, 6h, 5v), (3v, 4h, 5v), (2v, 2h, 4v)})
(8v, {(6v, 6h), (4v, 4h), (3v, 8h), (2v, 2h)}, {(8v, 6h), (7v, 4h), (6v, 8h), (6v, 2h)}, {(6v, 6h, 7v), (4v, 4h, 6v), (3v, 8h, 5v), (2v, 2h, 5v)})
(9v, {(7v, 4h), (6v, 6h), (3v, 2h), (2v, 8h)}, {(9v, 4h), (8v, 6h), (7v, 2h), (6v, 8h)}, {(7v, 4h, 8v), (6v, 6h, 7v), (3v, 2h, 6v), (2v, 8h, 5v)})
(11v, {(10v, 6h), (7v, 8h), (3v, 4h), (2v, 2h)}, ?, ?)