fff ffi ffk ffr ffs fif fii fik fir fis fkf fki fkk frf fri frk frr frs fsf fsi fsk fsr fss i-f iff ifi ifr ifs iif iii iir iis ikf iki ikk ikr iks ir- irf iri irk irr irs is- isf isi isk isr iss kff kfi kfs kif kii kik kir kis kki kkk kkr kks krf kri krk krr krs ksf ksi ksk ksr kss rff rfi rfk rfr rfs rif rii rik rir ris rkf rkk rks rrf rri rrk rrr rrs rsf rsi rsk rsr rss sff sfi sfk sfr sfs sif sii sik sir sis sk- skf ski skk skr sks sr- srf sri srk srr srs ss- ssf ssi ssk ssr sss