ddd dde dds ddt ddx de- ded dee des det dex dsd dse dss dst dsx dtd dte dts dtt dtx dxd dxs dxt dxx ed- edd ede eds edt edx eed eee ees eet eex es- esd ese ess est esx etd ete ets ett etx ex- exd exe exs ext exx sdd sde sds sdt se- sed see ses set sex ss- ssd sse sss sst ssx std ste sts stt stx sxs sxt t-x tdd tde tds tdt tdx te- ted tee tes tet tex tsd tse tss tst tsx ttd tte tts ttt ttx txe txs txt xde xds xdt xed xee xes xet xex xss xst xts xtx xxx