a-a a-b a-c aaa aab aac aae aaf aak aas ab- aba abb abc abe abf abk abs ac- aca acb acc ace acf ack acs aea aeb aec aee aef aek aes af- afa afb afc afe aff afk afs aka akb akc ake akk aks as- asa asb asc ase asf ask ass baa bab bac bae baf bak bas bba bbb bbc bbe bbf bbk bbs bca bcb bcc bce bcf bck bcs be- bea beb bec bee bef bek bes bfa bfb bfc bfe bff bfs bka bkb bkc bke bkf bkk bks bsa bsb bsc bse bsf bsk bss c-- caa cab cac cae caf cak cas cba cbb cbc cbe cbf cbk cbs cca ccb ccc cce ccf cck ccs ce- cea ceb cec cee cef cek ces cfa cfb cfc cfe cff cfk cfs cka ckb ckc cks csa csb csc cse csf csk css eaa eab eac eae eaf eak eas eba ebb ebc ebe ebf ebk ebs ec- eca ecb ecc ece ecf eck ecs eea eeb eec eee eef eek ees ef- efa efb efc efe eff efs eka ekb ekc eke ekf eks es- esa esb esc ese esf esk ess faa fab fac fae faf fak fas fba fbb fbc fbe fbf fbk fbs fca fcb fcc fce fcf fck fcs fea feb fec fee fef fek fes ffa ffc ffe fff ffk ffs fka fkb fkc fkf fkk fsa fsb fsc fse fsf fsk fss ka- kaa kab kac kae kaf kak kas kba kbb kbc kbe kbf kbk kbs kca kcb kcc kce kck kcs ke- kea keb kec kee kef kek kes kfa kfc kff kfs kkb kkc kke kkk kks ksa ksb ksc kse ksf ksk kss saa sab sac sae saf sak sas sba sbb sbc sbe sbf sbk sbs sca scb scc sce scf sck scs se- sea seb sec see sef sek ses sfa sfb sfc sfe sff sfk sfs sk- ska skb skc ske skf skk sks ss- ssa ssb ssc sse ssf ssk sss