-er a-a a-b a-i aaa aab aae aai aak aao aar ab- aba abb abe abi abk abo abr aea aeb aee aei aek aeo aer ai- aia aib aie aii aik aio air aka akb ake aki akk ako akr aoa aob aoe aoi aok aoo aor ar- ara arb are ari ark aro arr baa bab bae bai bak bao bar bba bbb bbe bbi bbk bbo bbr be- bea beb bee bei bek beo ber bi- bia bib bie bii bik bio bir bka bkb bke bkk bko bkr boa bob boe boi bok boo bor bra brb bre bri brk bro brr eaa eab eae eai eak eao ear eba ebb ebe ebi ebk ebo ebr eea eeb eee eek eeo eer eia eib eie eii eik eio eir eka ekb eke eki eko ekr eo- eoa eob eoe eoi eok eoo eor era erb ere eri erk ero err ia- iaa iab iae iai iao iar iba ibb ibe ibi ibk ibo ibr ie- iea iee iei iek ier iia iib iie iii iio iir ika ikb ike iki ikk iko ikr io- ioa iob ioe ioi ioo ior ir- ira irb ire iri irk iro irr ka- kaa kab kae kai kak kao kar kba kbb kbe kbi kbk kbo kbr ke- kea keb kee kei kek keo ker kia kib kie kii kik kio kir kkb kke kki kkk kkr koa kob koe koi kok koo kor kra kri krk kro krr o-i oaa oab oae oai oak oao oar ob- oba obb obe obi obk obo obr oea oeb oee oei oeo oer oia oib oie oii oik oio oir oka okb oke oki okk oko okr oo- ooa oob ooi ook ooo oor or- ora orb ore ori ork oro orr ra- raa rab rae rai rak rao rar rba rbb rbe rbi rbk rbo rbr re- rea reb ree rei rek reo rer ria rib rie rii rik rio rir rkb rke rkk rko roa rob roe roi rok roo ror rra rrb rri rrk rrr