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