12
3 9 5 2       // vertex 0's neighbors
11 0 4 7      // vertex 1's neighbors 
              // vertex 2's neighbors (none)
0 1 4 9 6     // vertex 3's ...
9 2 4 5 1 0   // vertex 4's ...
0 4 7 9 10 11 // vertex 5's ...
1 3 7         // vertex 6's ...
8 2 1         // vertex 7's ...
7 0 10 11     // vertex 8's ...
0 1 2 3 4 5   // vertex 9's ...
3 4 9 11      // vertex 10's ...
5             // vertex 11's ...