a-a a-b aaa aab aak aao aar aau aav ab- aba abb abk abo abr abu abv aka akb akk ako akr aku akv aoa aob aok aoo aor aou aov ar- ara arb ark aro arr aru arv au- aua aub auk auo aur auv av- ava avb avk avo avr avu b-u baa bab bak bao bar bau bav bba bbb bbk bbo bbr bbu bka bkb bkk bko bkr bkv boa bob bok boo bor bou bov bra brb brk bro brr bru brv bua bub buk buo bur buu bva bvb bvk bvo bvr bvu bvv ka- kaa kab kak kao kar kau kav kba kbb kbk kbo kbr kbu kkb kkk kkr kku kkv koa kob kok koo kor kou kra krk kro krr kru krv kub kuk kur kuu kva kvb kvk kvo kvr kvv oaa oab oak oao oar oau oav ob- oba obb obk obo obr obu obv oka okb okk oko okr oku oo- ooa oob ook ooo oor oov or- ora orb ork oro orr oru orv ou- oua ouk ouo our ov- ova ovb ovo ovv ra- raa rab rak rao rar rau rav rba rbb rbk rbo rbr rbu rkb rkk rko rku rkv roa rob rok roo ror rou rov rra rrb rrk rrr rru rua rub ruk ruo rur ruu ruv rva rvb rvo rvr rvu rvv ua- uaa uab uak uao uar uau uav uba ubb ubk ubo ubr ubu ubv uka ukb ukk ukr uku uoa uob uok uoo uor ur- ura urb urk uro urr uru uua uur uuu uva uvb uvo uvu uvv v-a vaa vab vak vao var vau vav vba vbk vbo vbr vbv vka vkb voa vob vok voo vor vou vov vra vrb vrk vrr vru vuk vur vuv vva vvb vvo vvr vvv