-er a-a a-b aaa aab aae aak aan aao aar ab- aba abb abe abk abn abo abr aea aeb aee aek aen aeo aer aka akb ake akk akn ako akr an- ana anb ane ank ann ano anr aoa aob aoe aok aon aoo aor ar- ara arb are ark arn aro arr baa bab bae bak ban bao bar bba bbb bbe bbk bbn bbo bbr be- bea beb bee bek ben beo ber bka bkb bke bkk bkn bko bkr bna bnb bne bnk bnn bno bnr boa bob boe bok bon boo bor bra brb bre brk brn bro brr eaa eab eae eak ean eao ear eba ebb ebe ebk ebn ebo ebr eea eeb eee eek een eeo eer eka ekb eke eko ekr en- ena enb ene enk enn eno enr eo- eoa eob eoe eok eon eoo eor era erb ere erk ern ero err ka- kaa kab kae kak kan kao kar kba kbb kbe kbk kbn kbo kbr ke- kea keb kee kek ken keo ker kkb kke kkk kkn kkr kn- kna kne knk knn kno knr koa kob koe kok kon koo kor kra krk krn kro krr naa nab nae nak nan nao nar nba nbb nbe nbk nbn nbo nbr ne- nea neb nee nek nen neo ner nka nke nkk nkn nko nkr nna nnb nne nnk nnn nno no- noa nob noe nok non noo nor nra nrb nre nrk nrn nro nrr oaa oab oae oak oan oao oar ob- oba obb obe obk obn obo obr oea oeb oee oen oeo oer oka okb oke okk oko okr on- ona onb one onk onn ono onr oo- ooa oob ook oon ooo oor or- ora orb ore ork orn oro orr ra- raa rab rae rak ran rao rar rba rbb rbe rbk rbn rbo rbr re- rea reb ree rek ren reo rer rkb rke rkk rko rna rnb rnn rno rnr roa rob roe rok ron roo ror rra rrb rrk rrn rrr