fff ffi ffn ffs ffx fif fii fin fis fix fnf fni fnn fns fnx fsf fsi fsn fss fsx fxi fxs fxx i-f iff ifi ifn ifs ifx iif iii iin iis iix in- inf ini inn ins inx is- isf isi isn iss ixi ixn n-i nff nfi nfn nfs nif nii nin nis nix nnf nni nnn nns nsf nsi nsn nss nsx sff sfi sfn sfs sfx sif sii sin sis six snf sni snn sns ss- ssf ssi ssn sss ssx sxi sxn sxs xfn xfs xfx xii xin xis xix xns xsi xss xxi xxx