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