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