-er a-a a-b a-t aaa aab aae aak aao aar aat ab- aba abb abe abk abo abr abt aea aeb aee aek aeo aer aet aka akb ake akk ako akr aoa aob aoe aok aoo aor aot ar- ara arb are ark aro arr art at- ata atb ate ato atr att baa bab bae bak bao bar bat bba bbb bbe bbk bbo bbr bbt be- bea beb bee bek beo ber bet bka bkb bke bkk bko bkr bkt boa bob boe bok boo bor bot bra brb bre brk bro brr brt bta btb bte btk bto btr btt eaa eab eae eak eao ear eat eba ebb ebe ebk ebo ebr ebt eea eeb eee eek eeo eer eet eka ekb eke eko ekr ekt eo- eoa eob eoe eok eoo eor eot era erb ere erk ero err ert eta etb ete etk eto etr ett k-t ka- kaa kab kae kak kao kar kat kba kbb kbe kbk kbo kbr ke- kea keb kee kek keo ker ket kkb kke kkk kkr kkt koa kob koe kok koo kor kot kra krk kro krr krt kta ktb kte ktk kto ktr ktt oaa oab oae oak oao oar oat ob- oba obb obe obk obo obr obt oea oeb oee oeo oer oet oka okb oke okk oko okr oo- ooa oob ook ooo oor oot or- ora orb ore ork oro orr ort ot- ota otb ote otk oto otr ott ra- raa rab rae rak rao rar rat rba rbb rbe rbk rbo rbr rbt re- rea reb ree rek reo rer ret rkb rke rkk rko rkt roa rob roe rok roo ror rot rra rrb rrk rrr rrt rta rtb rte rtk rto rtr rtt taa tab tae tak tao tar tat tba tbb tbe tbk tbo tbr tbt te- tea teb tee tek teo ter tet tka tkb tke tkk tko tkr tkt to- toa tob toe tok too tor tot tra trb tre trk tro trr trt tta ttb tte ttk tto ttr ttt