-er a-a a-b aaa aab aad aae aak aan aao aar ab- aba abb abd abe abk abn abo abr ad- ada adb add ade adk adn ado adr aea aeb aed aee aek aen aeo aer aka akb akd ake akk akn ako akr an- ana anb and ane ank ann ano anr aoa aob aod aoe aok aon aoo aor ar- ara arb ard are ark arn aro arr baa bab bad bae bak ban bao bar bba bbb bbd bbe bbk bbn bbo bbr bda bdb bdd bde bdk bdo bdr be- bea beb bed bee bek ben beo ber bka bkb bke bkk bkn bko bkr bna bnb bnd bne bnk bnn bno bnr boa bob bod boe bok bon boo bor bra brb brd bre brk brn bro brr daa dab dad dae dak dan dao dar dba dbb dbd dbe dbk dbn dbo dbr dda ddb ddd dde ddk ddn ddo ddr de- dea deb ded dee dek den deo der dka dkb dke dkk dko dkr dna dnb dnd dne dnk dnn dno dnr doa dob dod doe dok don doo dor dra drb drd dre drk drn dro drr eaa eab ead eae eak ean eao ear eba ebb ebd ebe ebk ebn ebo ebr ed- eda edb edd ede edk edn edo edr eea eeb eed eee eek een eeo eer eka ekb ekd eke eko ekr en- ena enb end ene enk enn eno enr eo- eoa eob eod eoe eok eon eoo eor era erb erd ere erk ern ero err ka- kaa kab kad kae kak kan kao kar kba kbb kbd kbe kbk kbn kbo kbr kda kdb kde kdk kdo kdr ke- kea keb ked kee kek ken keo ker kkb kke kkk kkn kkr kn- kna knd kne knk knn kno knr koa kob kod koe kok kon koo kor kra krd krk krn kro krr naa nab nad nae nak nan nao nar nba nbb nbd nbe nbk nbn nbo nbr nda ndb ndd nde ndk ndn ndo ndr ne- nea neb ned nee nek nen neo ner nka nke nkk nkn nko nkr nna nnb nne nnk nnn nno no- noa nob nod noe nok non noo nor nra nrb nrd nre nrk nrn nro nrr oaa oab oad oae oak oan oao oar ob- oba obb obd obe obk obn obo obr oda odb odd ode odn odo odr oea oeb oed oee oen oeo oer oka okb okd oke okk oko okr on- ona onb ond one onk onn ono onr oo- ooa oob ood ook oon ooo oor or- ora orb ord ore ork orn oro orr ra- raa rab rad rae rak ran rao rar rba rbb rbd rbe rbk rbn rbo rbr rda rdb rdd rde rdn rdo rdr re- rea reb red ree rek ren reo rer rkb rke rkk rko rna rnb rnd rnn rno rnr roa rob rod roe rok ron roo ror rra rrb rrd rrk rrn rrr