-er a-a a-b a-c aaa aab aac aae aak aao aar aav ab- aba abb abc abe abk abo abr abv ac- aca acb acc ace ack aco acr acv aea aeb aec aee aek aeo aer aev aka akb akc ake akk ako akr akv aoa aob aoc aoe aok aoo aor aov ar- ara arb arc are ark aro arr arv av- ava avb avc ave avk avo avr baa bab bac bae bak bao bar bav bba bbb bbc bbe bbk bbo bbr bca bcb bcc bce bck bco bcr bcv be- bea beb bec bee bek beo ber bev bka bkb bkc bke bkk bko bkr bkv boa bob boc boe bok boo bor bov bra brb bre brk bro brr brv bva bvb bvc bve bvk bvo bvr bvv c-- caa cab cac cae cak cao car cav cba cbb cbc cbe cbk cbo cbr cbv cca ccb ccc cce cck cco ccr ccv ce- cea ceb cec cee cek ceo cer cev cka ckb ckc cko co- coa cob coc coe cok coo cor cov cra crb crc cre crk cro crr crv cva cvb cvc cve cvk cvo cvr cvv eaa eab eac eae eak eao ear eav eba ebb ebc ebe ebk ebo ebr ebv ec- eca ecb ecc ece eck eco ecr ecv eea eeb eec eee eek eeo eer eev eka ekb ekc eke eko ekr ekv eo- eoa eob eoc eoe eok eoo eor era erb erc ere erk ero err erv eva evb evc eve evo evr evv ka- kaa kab kac kae kak kao kar kav kba kbb kbc kbe kbk kbo kbr kca kcb kcc kce kck kcr ke- kea keb kec kee kek keo ker kev kkb kkc kke kkk kkr kkv koa kob koc koe kok koo kor kra krc krk kro krr krv kva kvb kvk kvo kvr kvv oaa oab oac oae oak oao oar oav ob- oba obb obc obe obk obo obr obv oc- oca ocb occ ock oco ocr ocv oea oeb oec oee oeo oer oka okb okc oke okk oko okr oo- ooa oob ooc ook ooo oor oov or- ora orb orc ore ork oro orr orv ov- ova ovb ovc ove ovo ovv ra- raa rab rac rae rak rao rar rav rba rbb rbc rbe rbk rbo rbr rca rcb rcc rce rco rcr rcv re- rea reb rec ree rek reo rer rev rkb rkc rke rkk rko rkv roa rob roc roe rok roo ror rov rra rrb rrc rrk rrr rva rvb rvc rve rvo rvr rvv v-a v-e vaa vab vac vae vak vao var vav vba vbc vbk vbo vbr vbv vca vcc vce vco vcr vea veb vec vee vek veo ver vka vkb voa vob voc voe vok voo vor vov vra vrb vrc vre vrk vrr vva vvb vvc vvo vvr vvv