a-a a-b a-t aaa aab aae aas aat aax ab- aba abb abe abs abt abx aea aeb aee aes aet aex as- asa asb ase ass ast asx at- ata atb ate ats att atx ax- axa axe axs axt axx baa bab bae bas bat bax bba bbb bbe bbs bbt bbx be- bea beb bee bes bet bex bsa bsb bse bss bst bsx bta btb bte bts btt btx bxb bxx eaa eab eae eas eat eax eba ebb ebe ebs ebt ebx eea eeb eee ees eet eex es- esa esb ese ess est esx eta etb ete ets ett etx ex- exa exe exs ext exx saa sab sae sas sat sax sba sbb sbe sbs sbt sbx se- sea seb see ses set sex ss- ssa ssb sse sss sst ssx sta stb ste sts stt stx sxs sxt t-x taa tab tae tas tat tax tba tbb tbe tbs tbt te- tea teb tee tes tet tex tsa tsb tse tss tst tsx tta ttb tte tts ttt ttx txe txs txt xaa xas xat xbe xbx xee xes xet xex xsa xsb xss xst xts xtx xxx