-er a-a a-b a-c aaa aab aac aad aae aak aao aar ab- aba abb abc abd abe abk abo abr ac- aca acb acc acd ace ack aco acr ad- ada adb adc add ade adk ado adr aea aeb aec aed aee aek aeo aer aka akb akc akd ake akk ako akr aoa aob aoc aod aoe aok aoo aor ar- ara arb arc ard are ark aro arr baa bab bac bad bae bak bao bar bba bbb bbc bbd bbe bbk bbo bbr bca bcb bcc bcd bce bck bco bcr bda bdb bdc bdd bde bdk bdo bdr be- bea beb bec bed bee bek beo ber bka bkb bkc bke bkk bko bkr boa bob boc bod boe bok boo bor bra brb brd bre brk bro brr c-- caa cab cac cad cae cak cao car cba cbb cbc cbd cbe cbk cbo cbr cca ccb ccc ccd cce cck cco ccr cda cdb cdc cdd cde cdk cdo cdr ce- cea ceb cec ced cee cek ceo cer cka ckb ckc ckd cko co- coa cob coc cod coe cok coo cor cra crb crc crd cre crk cro crr daa dab dac dad dae dak dao dar dba dbb dbc dbd dbe dbk dbo dbr dca dcb dcc dcd dce dck dco dcr dda ddb ddc ddd dde ddk ddo ddr de- dea deb dec ded dee dek deo der dka dkb dkc dke dkk dko dkr doa dob doc dod doe dok doo dor dra drb drc drd dre drk dro drr eaa eab eac ead eae eak eao ear eba ebb ebc ebd ebe ebk ebo ebr ec- eca ecb ecc ecd ece eck eco ecr ed- eda edb edc edd ede edk edo edr eea eeb eec eed eee eek eeo eer eka ekb ekc ekd eke eko ekr eo- eoa eob eoc eod eoe eok eoo eor era erb erc erd ere erk ero err ka- kaa kab kac kad kae kak kao kar kba kbb kbc kbd kbe kbk kbo kbr kca kcb kcc kcd kce kck kcr kda kdb kdc kde kdk kdo kdr ke- kea keb kec ked kee kek keo ker kkb kkc kke kkk kkr koa kob koc kod koe kok koo kor kra krc krd krk kro krr oaa oab oac oad oae oak oao oar ob- oba obb obc obd obe obk obo obr oc- oca ocb occ ocd ock oco ocr oda odb odc odd ode odo odr oea oeb oec oed oee oeo oer oka okb okc okd oke okk oko okr oo- ooa oob ooc ood ook ooo oor or- ora orb orc ord ore ork oro orr ra- raa rab rac rad rae rak rao rar rba rbb rbc rbd rbe rbk rbo rbr rca rcb rcc rcd rce rco rcr rda rdb rdc rdd rde rdo rdr re- rea reb rec red ree rek reo rer rkb rkc rke rkk rko roa rob roc rod roe rok roo ror rra rrb rrc rrd rrk rrr