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