eee eef eek eeo eep ees ef- efe eff efo efp efs eke ekf eko ekp eks eo- eoe eof eok eoo eop eos ep- epe epf epo epp eps es- ese esf esk eso esp ess fee fef fek feo fep fes ffe fff ffk ffo ffp ffs fkf fkk fkp foe fof fok foo fop fos fpe fpk fpo fpp fps fse fsf fsk fso fsp fss ke- kee kef kek keo kep kes kff kfo kfs kke kkk kkp kks koe kof kok koo kop kos kpe kpf kpk kpo kpp kps kse ksf ksk kso ksp kss oee oef oeo oep oes of- ofe off ofo ofp ofs oke okk oko okp oks oo- oof ook ooo oop oos op- ope opf opk opo opp ops os- ose osf osk oso osp oss p-p pee pef pek peo pep pes pfe pff pfk pfo pfp pfs pke pkf pko pkp pks poe pof pok poo pop pos ppe ppf ppk ppo ppp pps ps- pse psf psk pso psp pss se- see sef sek seo sep ses sfe sff sfk sfo sfp sfs sk- ske skf skk sko skp sks soe sof sok soo sop sos spe spf spk spo spp sps ss- sse ssf ssk sso ssp sss