[(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),(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)]
