a-a a-b a-t aaa aab aae aaf aak aas aat ab- aba abb abe abf abk abs abt aea aeb aee aef aek aes aet af- afa afb afe aff afk afs aft aka akb ake akk aks as- asa asb ase asf ask ass ast at- ata atb ate atf ats att baa bab bae baf bak bas bat bba bbb bbe bbf bbk bbs bbt be- bea beb bee bef bek bes bet bfa bfb bfe bff bfs bft bka bkb bke bkf bkk bks bkt bsa bsb bse bsf bsk bss bst bta btb bte btf btk bts btt eaa eab eae eaf eak eas eat eba ebb ebe ebf ebk ebs ebt eea eeb eee eef eek ees eet ef- efa efb efe eff efs eft eka ekb eke ekf eks ekt es- esa esb ese esf esk ess est eta etb ete etf etk ets ett faa fab fae faf fak fas fat fba fbb fbe fbf fbk fbs fbt fea feb fee fef fek fes fet ffa ffe fff ffk ffs fft fka fkb fkf fkk fkt fsa fsb fse fsf fsk fss fst fta ftb fte ftf ftk fts ftt k-t ka- kaa kab kae kaf kak kas kat kba kbb kbe kbf kbk kbs ke- kea keb kee kef kek kes ket kfa kff kfs kkb kke kkk kks kkt ksa ksb kse ksf ksk kss kst kta ktb kte ktf ktk kts ktt saa sab sae saf sak sas sat sba sbb sbe sbf sbk sbs sbt se- sea seb see sef sek ses set sfa sfb sfe sff sfk sfs sft sk- ska skb ske skf skk sks skt ss- ssa ssb sse ssf ssk sss sst sta stb ste stf stk sts stt taa tab tae taf tak tas tat tba tbb tbe tbf tbk tbs tbt te- tea teb tee tef tek tes tet tfa tfb tfe tff tfk tfs tft tka tkb tke tkk tks tkt tsa tsb tse tsf tsk tss tst tta ttb tte ttf ttk tts ttt