-er a-a a-b a-c aaa aab aac aae aam aao aar ab- aba abb abc abe abm abo abr ac- aca acb acc ace acm aco acr aea aeb aec aee aem aeo aer ama amb amc ame amm amo amr aoa aob aoc aoe aom aoo aor ar- ara arb arc are arm aro arr baa bab bac bae bam bao bar bba bbb bbc bbe bbm bbo bbr bca bcb bcc bce bcm bco bcr be- bea beb bec bee bem beo ber bma bmb bmc bme bmm bmo bmr boa bob boc boe bom boo bor bra brb bre brm bro brr c-- caa cab cac cae cam cao car cba cbb cbc cbe cbm cbo cbr cca ccb ccc cce ccm cco ccr ce- cea ceb cec cee cem ceo cer cma cmb cmc cme cmm cmo cmr co- coa cob coc coe com coo cor cra crb crc cre crm cro crr eaa eab eac eae eam eao ear eba ebb ebc ebe ebm ebo ebr ec- eca ecb ecc ece ecm eco ecr eea eeb eec eee eem eeo eer em- ema emb emc eme emm emo emr eo- eoa eob eoc eoe eom eoo eor era erb erc ere erm ero err m-o m-r maa mab mac mae mam mao mar mba mbb mbc mbe mbm mbo mbr mc- mca mcb mcc mce mcm mco mcr mea meb mec mee mem meo mer mma mmb mmc mme mmm mmo mmr moa mob moc moe mom moo mor mra mrb mrc mre mrm mro mrr oaa oab oac oae oam oao oar ob- oba obb obc obe obm obo obr oc- oca ocb occ ocm oco ocr oea oeb oec oee oem oeo oer om- oma omb omc ome omm omo omr oo- ooa oob ooc oom ooo oor or- ora orb orc ore orm oro orr ra- raa rab rac rae ram rao rar rba rbb rbc rbe rbm rbo rbr rca rcb rcc rce rcm rco rcr re- rea reb rec ree rem reo rer rma rmb rmc rme rmm rmo rmr roa rob roc roe rom roo ror rra rrb rrc rrm rrr