a-a a-b a-t aaa aab aae aak aas aat ab- aba abb abe abk abs abt aea aeb aee aek aes aet aka akb ake akk aks as- asa asb ase ask ass ast at- ata atb ate ats att baa bab bae bak bas bat bba bbb bbe bbk bbs bbt be- bea beb bee bek bes bet bka bkb bke bkk bks bkt bsa bsb bse bsk bss bst bta btb bte btk bts btt eaa eab eae eak eas eat eba ebb ebe ebk ebs ebt eea eeb eee eek ees eet eka ekb eke eks ekt es- esa esb ese esk ess est eta etb ete etk ets ett k-t ka- kaa kab kae kak kas kat kba kbb kbe kbk kbs ke- kea keb kee kek kes ket kkb kke kkk kks kkt ksa ksb kse ksk kss kst kta ktb kte ktk kts ktt saa sab sae sak sas sat sba sbb sbe sbk sbs sbt se- sea seb see sek ses set sk- ska skb ske skk sks skt ss- ssa ssb sse ssk sss sst sta stb ste stk sts stt taa tab tae tak tas tat tba tbb tbe tbk tbs tbt te- tea teb tee tek tes tet tka tkb tke tkk tks tkt tsa tsb tse tsk tss tst tta ttb tte ttk tts ttt