-er ddd dde ddr dds ddt ddx de- ded dee der des det dex drd dre drr drs drt drx dsd dse dsr dss dst dsx dtd dte dtr dts dtt dtx dxd dxr dxs dxt dxx ed- edd ede edr eds edt edx eed eee eer ees eet eex erd ere err ers ert es- esd ese esr ess est esx etd ete etr ets ett etx ex- exd exe exr exs ext exx rdd rde rdr rds rdt rdx re- red ree rer res ret rex rrd rrr rrs rrt rsd rse rsr rss rst rsx rtd rte rtr rts rtt rtx rxr rxs sdd sde sdr sds sdt se- sed see ser ses set sex sr- srd sre srr srs srt srx ss- ssd sse ssr sss sst ssx std ste str sts stt stx sxs sxt t-x tdd tde tdr tds tdt tdx te- ted tee ter tes tet tex trd tre trr trs trt trx tsd tse tsr tss tst tsx ttd tte ttr tts ttt ttx txe txs txt xde xdr xds xdt xed xee xer xes xet xex xrd xrt xrx xss xst xtr xts xtx xxx