[(0,1),(1,2),(1,3),(2,4),(4,5),(2,6),(5,7),(3,7),(7,8),(3,9),(8,10),(10,11),(4,12),(6,13),(9,14),(8,15),(5,16),(6,17),(0,18),(10,19),(9,20)]
[(0,1),(1,2),(0,3),(2,4),(1,5),(3,6),(5,6),(2,7),(5,8),(4,9),(7,10),(8,11),(6,12),(8,13),(9,14),(7,15),(10,16),(4,17),(10,18),(3,19),(9,20)]
