a-a a-b a-c aaa aab aac aae aaf aak aao aas ab- aba abb abc abe abf abk abo abs ac- aca acb acc ace acf ack aco acs aea aeb aec aee aef aek aeo aes af- afa afb afc afe aff afk afo afs aka akb akc ake akk ako aks aoa aob aoc aoe aof aok aoo aos as- asa asb asc ase asf ask aso ass baa bab bac bae baf bak bao bas bba bbb bbc bbe bbf bbk bbo bbs bca bcb bcc bce bcf bck bco bcs be- bea beb bec bee bef bek beo bes bfa bfb bfc bfe bff bfo bfs bka bkb bkc bke bkf bkk bko bks boa bob boc boe bof bok boo bos bsa bsb bsc bse bsf bsk bso bss c-- caa cab cac cae caf cak cao cas cba cbb cbc cbe cbf cbk cbo cbs cca ccb ccc cce ccf cck cco ccs ce- cea ceb cec cee cef cek ceo ces cfa cfb cfc cfe cff cfk cfo cfs cka ckb ckc cko cks co- coa cob coc coe cof cok coo cos csa csb csc cse csf csk cso css eaa eab eac eae eaf eak eao eas eba ebb ebc ebe ebf ebk ebo ebs ec- eca ecb ecc ece ecf eck eco ecs eea eeb eec eee eef eek eeo ees ef- efa efb efc efe eff efo efs eka ekb ekc eke ekf eko eks eo- eoa eob eoc eoe eof eok eoo eos es- esa esb esc ese esf esk eso ess faa fab fac fae faf fak fao fas fba fbb fbc fbe fbf fbk fbo fbs fca fcb fcc fce fcf fck fco fcs fea feb fec fee fef fek feo fes ffa ffc ffe fff ffk ffo ffs fka fkb fkc fkf fkk foa fob foc foe fof fok foo fos fsa fsb fsc fse fsf fsk fso fss ka- kaa kab kac kae kaf kak kao kas kba kbb kbc kbe kbf kbk kbo kbs kca kcb kcc kce kck kcs ke- kea keb kec kee kef kek keo kes kfa kfc kff kfo kfs kkb kkc kke kkk kks koa kob koc koe kof kok koo kos ksa ksb ksc kse ksf ksk kso kss oaa oab oac oae oaf oak oao oas ob- oba obb obc obe obf obk obo obs oc- oca ocb occ ocf ock oco ocs oea oeb oec oee oef oeo oes of- ofa ofb ofc ofe off ofo ofs oka okb okc oke okk oko oks oo- ooa oob ooc oof ook ooo oos os- osa osb osc ose osf osk oso oss saa sab sac sae saf sak sao sas sba sbb sbc sbe sbf sbk sbo sbs sca scb scc sce scf sck sco scs se- sea seb sec see sef sek seo ses sfa sfb sfc sfe sff sfk sfo sfs sk- ska skb skc ske skf skk sko sks soa sob soc soe sof sok soo sos ss- ssa ssb ssc sse ssf ssk sso sss