-er a-a a-b aaa aab aad aae aak aao aar ab- aba abb abd abe abk abo abr ad- ada adb add ade adk ado adr aea aeb aed aee aek aeo aer aka akb akd ake akk ako akr aoa aob aod aoe aok aoo aor ar- ara arb ard are ark aro arr baa bab bad bae bak bao bar bba bbb bbd bbe bbk bbo bbr bda bdb bdd bde bdk bdo bdr be- bea beb bed bee bek beo ber bka bkb bke bkk bko bkr boa bob bod boe bok boo bor bra brb brd bre brk bro brr daa dab dad dae dak dao dar dba dbb dbd dbe dbk dbo dbr dda ddb ddd dde ddk ddo ddr de- dea deb ded dee dek deo der dka dkb dke dkk dko dkr doa dob dod doe dok doo dor dra drb drd dre drk dro drr eaa eab ead eae eak eao ear eba ebb ebd ebe ebk ebo ebr ed- eda edb edd ede edk edo edr eea eeb eed eee eek eeo eer eka ekb ekd eke eko ekr eo- eoa eob eod eoe eok eoo eor era erb erd ere erk ero err ka- kaa kab kad kae kak kao kar kba kbb kbd kbe kbk kbo kbr kda kdb kde kdk kdo kdr ke- kea keb ked kee kek keo ker kkb kke kkk kkr koa kob kod koe kok koo kor kra krd krk kro krr oaa oab oad oae oak oao oar ob- oba obb obd obe obk obo obr oda odb odd ode odo odr oea oeb oed oee oeo oer oka okb okd oke okk oko okr oo- ooa oob ood ook ooo oor or- ora orb ord ore ork oro orr ra- raa rab rad rae rak rao rar rba rbb rbd rbe rbk rbo rbr rda rdb rdd rde rdo rdr re- rea reb red ree rek reo rer rkb rke rkk rko roa rob rod roe rok roo ror rra rrb rrd rrk rrr