-er a-a a-b aaa aab aae aak aao aar aav ab- aba abb abe abk abo abr abv aea aeb aee aek aeo aer aev aka akb ake akk ako akr akv aoa aob aoe aok aoo aor aov ar- ara arb are ark aro arr arv av- ava avb ave avk avo avr baa bab bae bak bao bar bav bba bbb bbe bbk bbo bbr be- bea beb bee bek beo ber bev bka bkb bke bkk bko bkr bkv boa bob boe bok boo bor bov bra brb bre brk bro brr brv bva bvb bve bvk bvo bvr bvv eaa eab eae eak eao ear eav eba ebb ebe ebk ebo ebr ebv eea eeb eee eek eeo eer eev eka ekb eke eko ekr ekv eo- eoa eob eoe eok eoo eor era erb ere erk ero err erv eva evb eve evo evr evv ka- kaa kab kae kak kao kar kav kba kbb kbe kbk kbo kbr ke- kea keb kee kek keo ker kev kkb kke kkk kkr kkv koa kob koe kok koo kor kra krk kro krr krv kva kvb kvk kvo kvr kvv oaa oab oae oak oao oar oav ob- oba obb obe obk obo obr obv oea oeb oee oeo oer oka okb oke okk oko okr oo- ooa oob ook ooo oor oov or- ora orb ore ork oro orr orv ov- ova ovb ove ovo ovv ra- raa rab rae rak rao rar rav rba rbb rbe rbk rbo rbr re- rea reb ree rek reo rer rev rkb rke rkk rko rkv roa rob roe rok roo ror rov rra rrb rrk rrr rva rvb rve rvo rvr rvv v-a v-e vaa vab vae vak vao var vav vba vbk vbo vbr vbv vea veb vee vek veo ver vka vkb voa vob voe vok voo vor vov vra vrb vre vrk vrr vva vvb vvo vvr vvv