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