In an undirected graph, (i,j) means that node i and node j are connected with an undirected edge.
The nodes are numbered from 0 to 8, and the edges are: (5,0) (8,7) (5,1) (1,0) (6,0) (6,1) (3,4) (1,7) (0,7) (1,8) (4,5) (2,7) (2,4) (5,2) (5,3).