a-a a-b a-c aaa aab aac aak aao aar aau aav ab- aba abb abc abk abo abr abu abv ac- aca acb acc ack aco acr acu acv aka akb akc akk ako akr aku akv aoa aob aoc aok aoo aor aou aov ar- ara arb arc ark aro arr aru arv au- aua aub auc auk auo aur auv av- ava avb avc avk avo avr avu b-u baa bab bac bak bao bar bau bav bba bbb bbc bbk bbo bbr bbu bca bcb bcc bck bco bcr bcu bcv bka bkb bkc bkk bko bkr bkv boa bob boc bok boo bor bou bov bra brb brk bro brr bru brv bua bub buc buk buo bur buu bva bvb bvc bvk bvo bvr bvu bvv c-- caa cab cac cak cao car cau cav cba cbb cbc cbk cbo cbr cbu cbv cca ccb ccc cck cco ccr ccu ccv cka ckb ckc cko co- coa cob coc cok coo cor cou cov cra crb crc crk cro crr cru crv cua cub cuc cuk cuo cur cuu cuv cva cvb cvc cvk cvo cvr cvu cvv ka- kaa kab kac kak kao kar kau kav kba kbb kbc kbk kbo kbr kbu kca kcb kcc kck kcr kcu kkb kkc kkk kkr kku kkv koa kob koc kok koo kor kou kra krc krk kro krr kru krv kub kuc kuk kur kuu kva kvb kvk kvo kvr kvv oaa oab oac oak oao oar oau oav ob- oba obb obc obk obo obr obu obv oc- oca ocb occ ock oco ocr ocu ocv oka okb okc okk oko okr oku oo- ooa oob ooc ook ooo oor oov or- ora orb orc ork oro orr oru orv ou- oua ouc ouk ouo our ov- ova ovb ovc ovo ovv ra- raa rab rac rak rao rar rau rav rba rbb rbc rbk rbo rbr rbu rca rcb rcc rco rcr rcu rcv rkb rkc rkk rko rku rkv roa rob roc rok roo ror rou rov rra rrb rrc rrk rrr rru rua rub ruc ruk ruo rur ruu ruv rva rvb rvc rvo rvr rvu rvv ua- uaa uab uac uak uao uar uau uav uba ubb ubc ubk ubo ubr ubu ubv uca ucb ucc uck uco ucr ucu ucv uka ukb ukc ukk ukr uku uoa uob uoc uok uoo uor ur- ura urb urc urk uro urr uru uua uuc uur uuu uva uvb uvc uvo uvu uvv v-a vaa vab vac vak vao var vau vav vba vbc vbk vbo vbr vbv vca vcc vco vcr vcu vka vkb voa vob voc vok voo vor vou vov vra vrb vrc vrk vrr vru vuk vur vuv vva vvb vvc vvo vvr vvv