fff ffi ffo ffp ffr ffs fif fii fip fir fis fof foi foo fop for fos fpi fpo fpp fpr fps frf fri fro frp frr frs fsf fsi fso fsp fsr fss i-f iff ifi ifo ifp ifr ifs iif iii iio iip iir iis io- iof ioi ioo iop ior ios ipf ipi ipo ipp ipr ips ir- irf iri iro irp irr irs is- isf isi iso isp isr iss o-i of- off ofi ofo ofp ofr ofs oif oii oio oip oir ois oo- oof ooi ooo oop oor oos op- opf opi opo opp opr ops or- orf ori oro orp orr ors os- osf osi oso osp osr oss p-p pff pfi pfo pfp pfr pfs pif pii pio pip pir pis pof poi poo pop por pos ppf ppi ppo ppp ppr pps prf pri pro prp prr prs ps- psf psi pso psp psr pss rff rfi rfo rfp rfr rfs rif rii rio rip rir ris rof roi roo rop ror ros rpf rpi rpo rpp rpr rps rrf rri rrp rrr rrs rsf rsi rso rsp rsr rss sff sfi sfo sfp sfr sfs sif sii sio sip sir sis sof soi soo sop sor sos spf spi spo spp spr sps sr- srf sri sro srp srr srs ss- ssf ssi sso ssp ssr sss