15..8
15..16
16..17
17..18
18..7
18..19
19..13
19..20
20..4
20..10
17..21
21..5
21..11
16..22
22..23
23..24
24..6
24..3
23..25
25..12
25..2
22..26
26..9
26..14
15..1

(8, (((7, (13, (4, 10))), (5, 11)), (((6, 3), (12, 2)), (9, 14))), 1)
(8, (((7, (13, 20)), 21), ((24, 25), 26)), 1)
(8, (((7, 19), 21), (23, 26)), 1)
(8, ((18, 21), 22), 1)
(8, (17, 22), 1)
(8, 16, 1)
(15)