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