-er a-a a-b aaa aab aae aag aak aao aar ab- aba abb abe abg abk abo abr aea aeb aee aeg aek aeo aer ag- aga agb age agg agk ago agr aka akb ake akg akk ako akr aoa aob aoe aog aok aoo aor ar- ara arb are arg ark aro arr baa bab bae bag bak bao bar bba bbb bbe bbg bbk bbo bbr be- bea beb bee beg bek beo ber bga bgb bge bgg bgk bgo bgr bka bkb bke bkg bkk bko bkr boa bob boe bog bok boo bor bra brb bre brg brk bro brr eaa eab eae eag eak eao ear eba ebb ebe ebg ebk ebo ebr eea eeb eee eeg eek eeo eer ega egb ege egg ego egr eka ekb eke ekg eko ekr eo- eoa eob eoe eog eok eoo eor era erb ere erg erk ero err gaa gab gae gag gak gao gar gba gbe gbg gbk gbo gbr ge- gea geb gee geg gek geo ger gga ggb ggg ggo ggr gka gkb gko goa gob goe gog gok goo gor gra grb gre grg grk gro grr ka- kaa kab kae kag kak kao kar kba kbb kbe kbk kbo kbr ke- kea keb kee keg kek keo ker kga kgb kgo kkb kke kkk kkr koa kob koe kog kok koo kor kra krg krk kro krr oaa oab oae oag oak oao oar ob- oba obb obe obg obk obo obr oea oeb oee oeg oeo oer oga oge ogg ogo oka okb oke okg okk oko okr oo- ooa oob oog ook ooo oor or- ora orb ore org ork oro orr ra- raa rab rae rag rak rao rar rba rbb rbe rbg rbk rbo rbr re- rea reb ree reg rek reo rer rga rgb rge rgg rgk rgo rgr rkb rke rkg rkk rko roa rob roe rog rok roo ror rra rrb rrg rrk rrr