-er eee eef eek eer ees ef- efe eff efi efr efs eie eif eii eik eir eis eke ekf eki ekr eks ere erf eri erk err ers es- ese esf esi esk esr ess fee fef fei fek fer fes ffe fff ffi ffk ffr ffs fie fif fii fik fir fis fkf fki fkk fre frf fri frk frr frs fse fsf fsi fsk fsr fss i-f ie- iee ief iei iek ier ies ife iff ifi ifr ifs iie iif iii iir iis ike ikf iki ikk ikr iks ir- ire irf iri irk irr irs is- ise isf isi isk isr iss ke- kee kef kei kek ker kes kff kfi kfs kie kif kii kik kir kis kke kki kkk kkr kks krf kri krk krr krs kse ksf ksi ksk ksr kss re- ree ref rei rek rer res rfe rff rfi rfk rfr rfs rie rif rii rik rir ris rke rkf rkk rks rrf rri rrk rrr rrs rse rsf rsi rsk rsr rss se- see sef sei sek ser ses sfe sff sfi sfk sfr sfs sie sif sii sik sir sis sk- ske skf ski skk skr sks sr- sre srf sri srk srr srs ss- sse ssf ssi ssk ssr sss