a-a a-b aaa aab aak aao aar aas aav ab- aba abb abk abo abr abs abv aka akb akk ako akr aks akv aoa aob aok aoo aor aos aov ar- ara arb ark aro arr ars arv as- asa asb ask aso asr ass asv av- ava avb avk avo avr avs baa bab bak bao bar bas bav bba bbb bbk bbo bbr bbs bka bkb bkk bko bkr bks bkv boa bob bok boo bor bos bov bra brb brk bro brr brs brv bsa bsb bsk bso bsr bss bsv bva bvb bvk bvo bvr bvs bvv ka- kaa kab kak kao kar kas kav kba kbb kbk kbo kbr kbs kkb kkk kkr kks kkv koa kob kok koo kor kos kra krk kro krr krs krv ksa ksb ksk kso ksr kss ksv kva kvb kvk kvo kvr kvs kvv oaa oab oak oao oar oas oav ob- oba obb obk obo obr obs obv oka okb okk oko okr oks oo- ooa oob ook ooo oor oos oov or- ora orb ork oro orr ors orv os- osa osb osk oso osr oss osv ov- ova ovb ovo ovs ovv ra- raa rab rak rao rar ras rav rba rbb rbk rbo rbr rbs rkb rkk rko rks rkv roa rob rok roo ror ros rov rra rrb rrk rrr rrs rsa rsb rsk rso rsr rss rsv rva rvb rvo rvr rvs rvv saa sab sak sao sar sas sav sba sbb sbk sbo sbr sbs sbv sk- ska skb skk sko skr sks soa sob sok soo sor sos sov sr- sra srb srk sro srr srs srv ss- ssa ssb ssk sso ssr sss ssv sva svb svk svo svr svs svv v-a vaa vab vak vao var vas vav vba vbk vbo vbr vbs vbv vka vkb voa vob vok voo vor vos vov vra vrb vrk vrr vrs vsa vsb vsk vso vsr vss vsv vva vvb vvo vvr vvs vvv