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