-er a-a a-b aaa aab aae aak aam aao aar ab- aba abb abe abk abm abo abr aea aeb aee aek aem aeo aer aka akb ake akk akm ako akr ama amb ame amk amm amo amr aoa aob aoe aok aom aoo aor ar- ara arb are ark arm aro arr baa bab bae bak bam bao bar bba bbb bbe bbk bbm bbo bbr be- bea beb bee bek bem beo ber bka bkb bke bkk bkm bko bkr bma bmb bme bmk bmm bmo bmr boa bob boe bok bom boo bor bra brb bre brk brm bro brr eaa eab eae eak eam eao ear eba ebb ebe ebk ebm ebo ebr eea eeb eee eek eem eeo eer eka ekb eke eko ekr em- ema emb eme emk emm emo emr eo- eoa eob eoe eok eom eoo eor era erb ere erk erm ero err ka- kaa kab kae kak kam kao kar kba kbb kbe kbk kbm kbo kbr ke- kea keb kee kek kem keo ker kkb kke kkk kkm kkr kma kmb kme kmk kmm kmo koa kob koe kok kom koo kor kra krk kro krr m-o m-r maa mab mae mak mam mao mar mba mbb mbe mbk mbm mbo mbr mea meb mee mek mem meo mer mka mkb mke mkk mkm mko mkr mma mmb mme mmk mmm mmo mmr moa mob moe mok mom moo mor mra mrb mre mrk mrm mro mrr oaa oab oae oak oam oao oar ob- oba obb obe obk obm obo obr oea oeb oee oem oeo oer oka okb oke okk oko okr om- oma omb ome omm omo omr oo- ooa oob ook oom ooo oor or- ora orb ore ork orm oro orr ra- raa rab rae rak ram rao rar rba rbb rbe rbk rbm rbo rbr re- rea reb ree rek rem reo rer rkb rke rkk rkm rko rma rmb rme rmm rmo rmr roa rob roe rok rom roo ror rra rrb rrk rrm rrr