a-a a-c a-t aaa aac aae aas aat aax ac- aca acc ace acs act acx aea aec aee aes aet aex as- asa asc ase ass ast asx at- ata atc ate ats att atx ax- axa axe axs axt axx c-- caa cac cae cas cat cax cca ccc cce ccs cct ccx ce- cea cec cee ces cet cex csa csc cse css cst csx cta ctc cte cts ctt ctx cxc cxs cxt cxx eaa eac eae eas eat eax ec- eca ecc ece ecs ect ecx eea eec eee ees eet eex es- esa esc ese ess est esx eta etc ete ets ett etx ex- exa exc exe exs ext exx saa sac sae sas sat sax sca scc sce scs sct scx se- sea sec see ses set sex ss- ssa ssc sse sss sst ssx sta stc ste sts stt stx sxc sxs sxt t-x taa tac tae tas tat tax tca tcc tce tcs tct tcx te- tea tec tee tes tet tex tsa tsc tse tss tst tsx tta ttc tte tts ttt ttx txe txs txt xaa xac xas xat xcx xee xes xet xex xsa xsc xss xst xtc xts xtx xxx