fff ffn ffo ffr ffs fnf fnn fnr fns fof fon foo for fos frf frn fro frr frs fsf fsn fso fsr fss nff nfn nfo nfr nfs nnf nnn nno nns no- nof non noo nor nos nrf nrn nro nrr nrs nsf nsn nso nsr nss of- off ofn ofo ofr ofs on- onf onn ono onr ons oo- oof oon ooo oor oos or- orf orn oro orr ors os- osf osn oso osr oss rff rfn rfo rfr rfs rnn rno rnr rns rof ron roo ror ros rrf rrn rrr rrs rsf rsn rso rsr rss sff sfn sfo sfr sfs snf snn sno snr sns sof son soo sor sos sr- srf srn sro srr srs ss- ssf ssn sso ssr sss