-er eee eef eek eer ees eet ef- efe eff efr efs eft eke ekf ekr eks ekt ere erf erk err ers ert es- ese esf esk esr ess est ete etf etk etr ets ett fee fef fek fer fes fet ffe fff ffk ffr ffs fft fkf fkk fkt fre frf frk frr frs frt fse fsf fsk fsr fss fst fte ftf ftk ftr fts ftt k-t ke- kee kef kek ker kes ket kff kfs kke kkk kkr kks kkt krf krk krr krs krt kse ksf ksk ksr kss kst kte ktf ktk ktr kts ktt re- ree ref rek rer res ret rfe rff rfk rfr rfs rft rke rkf rkk rks rkt rrf rrk rrr rrs rrt rse rsf rsk rsr rss rst rte rtf rtk rtr rts rtt se- see sef sek ser ses set sfe sff sfk sfr sfs sft sk- ske skf skk skr sks skt sr- sre srf srk srr srs srt ss- sse ssf ssk ssr sss sst ste stf stk str sts stt te- tee tef tek ter tes tet tfe tff tfk tfr tfs tft tke tkk tkr tks tkt tre trf trk trr trs trt tse tsf tsk tsr tss tst tte ttf ttk ttr tts ttt