a-a a-b a-c aaa aab aac aad aae aaf aak aao ab- aba abb abc abd abe abf abk abo ac- aca acb acc acd ace acf ack aco ad- ada adb adc add ade adf adk ado aea aeb aec aed aee aef aek aeo af- afa afb afc afd afe aff afk afo aka akb akc akd ake akk ako aoa aob aoc aod aoe aof aok aoo baa bab bac bad bae baf bak bao bba bbb bbc bbd bbe bbf bbk bbo bca bcb bcc bcd bce bcf bck bco bda bdb bdc bdd bde bdf bdk bdo be- bea beb bec bed bee bef bek beo bfa bfb bfc bfd bfe bff bfo bka bkb bkc bke bkf bkk bko boa bob boc bod boe bof bok boo c-- caa cab cac cad cae caf cak cao cba cbb cbc cbd cbe cbf cbk cbo cca ccb ccc ccd cce ccf cck cco cda cdb cdc cdd cde cdf cdk cdo ce- cea ceb cec ced cee cef cek ceo cfa cfb cfc cfd cfe cff cfk cfo cka ckb ckc ckd cko co- coa cob coc cod coe cof cok coo daa dab dac dad dae daf dak dao dba dbb dbc dbd dbe dbf dbk dbo dca dcb dcc dcd dce dcf dck dco dda ddb ddc ddd dde ddf ddk ddo de- dea deb dec ded dee def dek deo dfa dfb dfc dfd dfe dff dfk dfo dka dkb dkc dke dkk dko doa dob doc dod doe dof dok doo eaa eab eac ead eae eaf eak eao eba ebb ebc ebd ebe ebf ebk ebo ec- eca ecb ecc ecd ece ecf eck eco ed- eda edb edc edd ede edf edk edo eea eeb eec eed eee eef eek eeo ef- efa efb efc efd efe eff efo eka ekb ekc ekd eke ekf eko eo- eoa eob eoc eod eoe eof eok eoo faa fab fac fad fae faf fak fao fba fbb fbc fbd fbe fbf fbk fbo fca fcb fcc fcd fce fcf fck fco fda fdb fdc fdd fde fdf fdk fdo fea feb fec fed fee fef fek feo ffa ffc ffd ffe fff ffk ffo fka fkb fkc fkf fkk foa fob foc foe fof fok foo ka- kaa kab kac kad kae kaf kak kao kba kbb kbc kbd kbe kbf kbk kbo kca kcb kcc kcd kce kck kda kdb kdc kde kdf kdk kdo ke- kea keb kec ked kee kef kek keo kfa kfc kfd kff kfo kkb kkc kke kkk koa kob koc kod koe kof kok koo oaa oab oac oad oae oaf oak oao ob- oba obb obc obd obe obf obk obo oc- oca ocb occ ocd ocf ock oco oda odb odc odd ode odf odo oea oeb oec oed oee oef oeo of- ofa ofb ofc ofd ofe off ofo oka okb okc okd oke okk oko oo- ooa oob ooc ood oof ook ooo