b-u bbb bbk bbn bbr bbu bkb bkk bkn bkr bnb bnk bnn bnr bnu brb brk brn brr bru bub buk bun bur buu kbb kbk kbn kbr kbu kkb kkk kkn kkr kku kn- knk knn knr knu krk krn krr kru kub kuk kun kur kuu nbb nbk nbn nbr nbu nkk nkn nkr nku nnb nnk nnn nnu nrb nrk nrn nrr nru nub nuk nun nur nuu rbb rbk rbn rbr rbu rkb rkk rku rnb rnn rnr rnu rrb rrk rrn rrr rru rub ruk run rur ruu ubb ubk ubn ubr ubu ukb ukk ukn ukr uku un- unb unk unn unr unu ur- urb urk urn urr uru uun uur uuu