fff ffi ffk ffo ffp ffs fif fii fik fip fis fkf fki fkk fkp fof foi fok foo fop fos fpi fpk fpo fpp fps fsf fsi fsk fso fsp fss i-f iff ifi ifo ifp ifs iif iii iio iip iis ikf iki ikk iko iks io- iof ioi ioo iop ios ipf ipi ipo ipp ips is- isf isi isk iso isp iss kff kfi kfo kfs kif kii kik kio kip kis kki kkk kkp kks kof koi kok koo kop kos kpf kpi kpk kpo kpp kps ksf ksi ksk kso ksp kss o-i of- off ofi ofo ofp ofs oif oii oik oio oip ois oki okk oko okp oks oo- oof ooi ook ooo oop oos op- opf opi opk opo opp ops os- osf osi osk oso osp oss p-p pff pfi pfk pfo pfp pfs pif pii pik pio pip pis pkf pki pko pkp pks pof poi pok poo pop pos ppf ppi ppk ppo ppp pps ps- psf psi psk pso psp pss sff sfi sfk sfo sfp sfs sif sii sik sio sip sis sk- skf ski skk sko skp sks sof soi sok soo sop sos spf spi spk spo spp sps ss- ssf ssi ssk sso ssp sss