16 24
0 1
0 4
1 2
1 5
2 3
2 6
3 7
4 5
4 8
5 6
5 9
6 7
6 10
7 11
8 9
8 12
9 10
9 13
10 11
10 14
11 15
12 13
13 14
14 15

Visual coupling graph:
 0--1--2--3
 |  |  |  |
 4--5--6--7
 |  |  |  |
 8--9-10-11
 |  |  |  |
12-13-14-15
