-er a-a a-b aaa aab aae aak aam aan aao aar ab- aba abb abe abk abm abn abo abr aea aeb aee aek aem aen aeo aer aka akb ake akk akm akn ako akr ama amb ame amk amm amn amo amr an- ana anb ane ank anm ann ano anr aoa aob aoe aok aom aon aoo aor ar- ara arb are ark arm arn aro arr baa bab bae bak bam ban bao bar bba bbb bbe bbk bbm bbn bbo bbr be- bea beb bee bek bem ben beo ber bka bkb bke bkk bkm bkn bko bkr bma bmb bme bmk bmm bmn bmo bmr bna bnb bne bnk bnn bno bnr boa bob boe bok bom bon boo bor bra brb bre brk brm brn bro brr eaa eab eae eak eam ean eao ear eba ebb ebe ebk ebm ebn ebo ebr eea eeb eee eek eem een eeo eer eka ekb eke eko ekr em- ema emb eme emk emm emn emo emr en- ena enb ene enk enm enn eno enr eo- eoa eob eoe eok eom eon eoo eor era erb ere erk erm ern ero err ka- kaa kab kae kak kam kan kao kar kba kbb kbe kbk kbm kbn kbo kbr ke- kea keb kee kek kem ken keo ker kkb kke kkk kkm kkn kkr kma kmb kme kmk kmm kmo kn- kna kne knk knm knn kno knr koa kob koe kok kom kon koo kor kra krk krn kro krr m-o m-r maa mab mae mak mam man mao mar mba mbb mbe mbk mbm mbo mbr mea meb mee mek mem men meo mer mka mkb mke mkk mkm mkn mko mkr mma mmb mme mmk mmm mmn mmo mmr mna mnb mne mnk mnm mnn mno mnr moa mob moe mok mom mon moo mor mra mrb mre mrk mrm mrn mro mrr naa nab nae nak nam nan nao nar nba nbb nbe nbk nbm nbn nbo nbr ne- nea neb nee nek nem nen neo ner nka nke nkk nkm nkn nko nkr nma nmb nme nmk nmm nmn nmo nmr nna nnb nne nnk nnm nnn nno no- noa nob noe nok nom non noo nor nra nrb nre nrk nrm nrn nro nrr oaa oab oae oak oam oan oao oar ob- oba obb obe obk obm obn obo obr oea oeb oee oem oen oeo oer oka okb oke okk oko okr om- oma omb ome omm omn omo omr on- ona onb one onk onn ono onr oo- ooa oob ook oom oon ooo oor or- ora orb ore ork orm orn oro orr ra- raa rab rae rak ram ran rao rar rba rbb rbe rbk rbm rbn rbo rbr re- rea reb ree rek rem ren reo rer rkb rke rkk rkm rko rma rmb rme rmm rmn rmo rmr rna rnb rnm rnn rno rnr roa rob roe rok rom ron roo ror rra rrb rrk rrm rrn rrr