b-u bbb bbk bbm bbr bbu bkb bkk bkm bkr bmb bmk bmm bmr bmu brb brk brm brr bru bub buk bum bur buu kbb kbk kbm kbr kbu kkb kkk kkm kkr kku kmb kmk kmm kmu krk krr kru kub kuk kum kur kuu m-r mbb mbk mbm mbr mbu mkb mkk mkm mkr mku mmb mmk mmm mmr mmu mrb mrk mrm mrr mru mub muk mum mur muu rbb rbk rbm rbr rbu rkb rkk rkm rku rmb rmm rmr rrb rrk rrm rrr rru rub ruk rum rur ruu ubb ubk ubr ubu ukb ukk ukr uku um- umb umm umr umu ur- urb urk urm urr uru uum uur uuu