4 :
(0,1,4),(1,5,3),(2,6,15),(3,7,1),(4,5,1),(4,8,9),(5,6,1),(5,9,2),(6,10,1),(7,11,23),(8,9,5),(8,12,7),(9,13,6),(10,14,3),(11,15,3),(12,13,4),(14,15,7)
