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