split 20 2 1 0
split 21 4 2 3
split 22 5 5 4
split 23 8 6 7
split 24 7 8 9
split 25 6 11 10
split 26 2 12 15
split 27 0 13 14
split 28 0 18 17
split 29 4 19 16
