-er ddd dde ddf ddr dds ddt de- ded dee def der des det dfd dfe dff dfr dfs dft drd dre drr drs drt dsd dse dsf dsr dss dst dtd dte dtf dtr dts dtt ed- edd ede edf edr eds edt eed eee eef eer ees eet ef- efd efe eff efr efs eft erd ere erf err ers ert es- esd ese esf esr ess est etd ete etf etr ets ett fdd fde fdf fdr fds fdt fed fee fef fer fes fet ffd ffe fff ffr ffs fft frd fre frf frr frs frt fsd fse fsf fsr fss fst ftd fte ftf ftr fts ftt rdd rde rdf rdr rds rdt re- red ree ref rer res ret rfd rfe rff rfr rfs rft rrd rrf rrr rrs rrt rsd rse rsf rsr rss rst rtd rte rtf rtr rts rtt sdd sde sdf sdr sds sdt se- sed see sef ser ses set sfd sfe sff sfr sfs sft sr- srd sre srf srr srs srt ss- ssd sse ssf ssr sss sst std ste stf str sts stt tdd tde tdf tdr tds tdt te- ted tee tef ter tes tet tfd tfe tff tfr tfs tft trd tre trf trr trs trt tsd tse tsf tsr tss tst ttd tte ttf ttr tts ttt