fff ffi ffo ffp ffs fif fii fip fis fof foi foo fop fos fpi fpo fpp fps fsf fsi fso fsp fss i-f iff ifi ifo ifp ifs iif iii iio iip iis io- iof ioi ioo iop ios ipf ipi ipo ipp ips is- isf isi iso isp iss o-i of- off ofi ofo ofp ofs oif oii oio oip ois oo- oof ooi ooo oop oos op- opf opi opo opp ops os- osf osi oso osp oss p-p pff pfi pfo pfp pfs pif pii pio pip pis pof poi poo pop pos ppf ppi ppo ppp pps ps- psf psi pso psp pss sff sfi sfo sfp sfs sif sii sio sip sis sof soi soo sop sos spf spi spo spp sps ss- ssf ssi sso ssp sss