a-a a-b a-c aaa aab aac aak aao aar aav ab- aba abb abc abk abo abr abv ac- aca acb acc ack aco acr acv aka akb akc akk ako akr akv aoa aob aoc aok aoo aor aov ar- ara arb arc ark aro arr arv av- ava avb avc avk avo avr baa bab bac bak bao bar bav bba bbb bbc bbk bbo bbr bca bcb bcc bck bco bcr bcv bka bkb bkc bkk bko bkr bkv boa bob boc bok boo bor bov bra brb brk bro brr brv bva bvb bvc bvk bvo bvr bvv c-- caa cab cac cak cao car cav cba cbb cbc cbk cbo cbr cbv cca ccb ccc cck cco ccr ccv cka ckb ckc cko co- coa cob coc cok coo cor cov cra crb crc crk cro crr crv cva cvb cvc cvk cvo cvr cvv ka- kaa kab kac kak kao kar kav kba kbb kbc kbk kbo kbr kca kcb kcc kck kcr kkb kkc kkk kkr kkv koa kob koc kok koo kor kra krc krk kro krr krv kva kvb kvk kvo kvr kvv oaa oab oac oak oao oar oav ob- oba obb obc obk obo obr obv oc- oca ocb occ ock oco ocr ocv oka okb okc okk oko okr oo- ooa oob ooc ook ooo oor oov or- ora orb orc ork oro orr orv ov- ova ovb ovc ovo ovv ra- raa rab rac rak rao rar rav rba rbb rbc rbk rbo rbr rca rcb rcc rco rcr rcv rkb rkc rkk rko rkv roa rob roc rok roo ror rov rra rrb rrc rrk rrr rva rvb rvc rvo rvr rvv v-a vaa vab vac vak vao var vav vba vbc vbk vbo vbr vbv vca vcc vco vcr vka vkb voa vob voc vok voo vor vov vra vrb vrc vrk vrr vva vvb vvc vvo vvr vvv