b-u bbb bbk bbn bbo bbr bbu bkb bkk bkn bko bkr bnb bnk bnn bno bnr bnu bob bok bon boo bor bou brb brk brn bro brr bru bub buk bun buo bur buu kbb kbk kbn kbo kbr kbu kkb kkk kkn kkr kku kn- knk knn kno knr knu kob kok kon koo kor kou krk krn kro krr kru kub kuk kun kur kuu nbb nbk nbn nbo nbr nbu nkk nkn nko nkr nku nnb nnk nnn nno nnu no- nob nok non noo nor nou nrb nrk nrn nro nrr nru nub nuk nun nuo nur nuu ob- obb obk obn obo obr obu okb okk oko okr oku on- onb onk onn ono onr onu oo- oob ook oon ooo oor or- orb ork orn oro orr oru ou- ouk oun ouo our rbb rbk rbn rbo rbr rbu rkb rkk rko rku rnb rnn rno rnr rnu rob rok ron roo ror rou rrb rrk rrn rrr rru rub ruk run ruo rur ruu ubb ubk ubn ubo ubr ubu ukb ukk ukn ukr uku un- unb unk unn uno unr unu uob uok uon uoo uor ur- urb urk urn uro urr uru uun uur uuu