fff ffi ffr ffs fft fif fii fir fis fit frf fri frr frs frt fsf fsi fsr fss fst ftf fti ftr fts ftt i-f iff ifi ifr ifs ift iif iii iir iis iit ir- irf iri irr irs irt is- isf isi isr iss ist itf iti its itt rff rfi rfr rfs rft rif rii rir ris rit rrf rri rrr rrs rrt rsf rsi rsr rss rst rtf rti rtr rts rtt sff sfi sfr sfs sft sif sii sir sis sit sr- srf sri srr srs srt ss- ssf ssi ssr sss sst stf sti str sts stt tff tfi tfr tfs tft tif tii tir tis tit trf tri trr trs trt tsf tsi tsr tss tst ttf tti ttr tts ttt