[(0,1),(1,2),(0,2),(1,3),(2,3),(3,4),(4,5),(5,6),(6,7),(5,7),(6,8),(7,8),(8,9),(4,10),(10,11),(10,12),(11,12),(9,13),(11,14),(12,15),(9,16),(13,17),(13,18)]
[(0,1),(0,2),(1,3),(2,3),(1,4),(2,4),(4,5),(3,6),(6,7),(5,8),(5,9),(7,9),(7,10),(9,10),(8,11),(10,11),(11,12),(6,13),(12,14),(13,15),(12,16),(13,17),(8,18)]
