[*([[[*(ab),*(cd)],e],[fg,*(hi)]]),x]
(0, (0, 0)) (1, (2, 15)) (2, (3, 13)) (3, (4, 8)) (4, (a, 5, 5)) (5, (b, 6, 6)) (6, (4, 7)) (7, (12, 12)) (8, (c, 9, 9)) (9, (d, 10, 10)) (10, (8, 11)) (11, (12, 12)) (12, (14, 14)) (13, (e, 14, 14)) (14, (23, 23)) (15, (16, 18)) (16, (f, 17, 17)) (17, (g, 22, 22)) (18, (h, 19, 19)) (19, (i, 20, 20)) (20, (18, 21)) (21, (22, 22)) (22, (23, 23)) (23, (24, 24)) (24, (1, 25)) (25, (26, 26)) (26, (x, 27, 27)) (27, (0, 0))