-er a-a a-b a-c aaa aab aac aae aak aam aao aar ab- aba abb abc abe abk abm abo abr ac- aca acb acc ace ack acm aco acr aea aeb aec aee aek aem aeo aer aka akb akc ake akk akm ako akr ama amb amc ame amk amm amo amr aoa aob aoc aoe aok aom aoo aor ar- ara arb arc are ark arm aro arr baa bab bac bae bak bam bao bar bba bbb bbc bbe bbk bbm bbo bbr bca bcb bcc bce bck bcm bco bcr be- bea beb bec bee bek bem beo ber bka bkb bkc bke bkk bkm bko bkr bma bmb bmc bme bmk bmm bmo bmr boa bob boc boe bok bom boo bor bra brb bre brk brm bro brr c-- caa cab cac cae cak cam cao car cba cbb cbc cbe cbk cbm cbo cbr cca ccb ccc cce cck ccm cco ccr ce- cea ceb cec cee cek cem ceo cer cka ckb ckc ckm cko cma cmb cmc cme cmk cmm cmo cmr co- coa cob coc coe cok com coo cor cra crb crc cre crk crm cro crr eaa eab eac eae eak eam eao ear eba ebb ebc ebe ebk ebm ebo ebr ec- eca ecb ecc ece eck ecm eco ecr eea eeb eec eee eek eem eeo eer eka ekb ekc eke eko ekr em- ema emb emc eme emk emm emo emr eo- eoa eob eoc eoe eok eom eoo eor era erb erc ere erk erm ero err ka- kaa kab kac kae kak kam kao kar kba kbb kbc kbe kbk kbm kbo kbr kca kcb kcc kce kck kcm kcr ke- kea keb kec kee kek kem keo ker kkb kkc kke kkk kkm kkr kma kmb kmc kme kmk kmm kmo koa kob koc koe kok kom koo kor kra krc krk kro krr m-o m-r maa mab mac mae mak mam mao mar mba mbb mbc mbe mbk mbm mbo mbr mc- mca mcb mcc mce mck mcm mco mcr mea meb mec mee mek mem meo mer mka mkb mkc mke mkk mkm mko mkr mma mmb mmc mme mmk mmm mmo mmr moa mob moc moe mok mom moo mor mra mrb mrc mre mrk mrm mro mrr oaa oab oac oae oak oam oao oar ob- oba obb obc obe obk obm obo obr oc- oca ocb occ ock ocm oco ocr oea oeb oec oee oem oeo oer oka okb okc oke okk oko okr om- oma omb omc ome omm omo omr oo- ooa oob ooc ook oom ooo oor or- ora orb orc ore ork orm oro orr ra- raa rab rac rae rak ram rao rar rba rbb rbc rbe rbk rbm rbo rbr rca rcb rcc rce rcm rco rcr re- rea reb rec ree rek rem reo rer rkb rkc rke rkk rkm rko rma rmb rmc rme rmm rmo rmr roa rob roc roe rok rom roo ror rra rrb rrc rrk rrm rrr