fff ffi ffk ffp ffx fif fii fik fip fix fkf fki fkk fkp fpi fpk fpp fpx fxi fxp fxx i-f iff ifi ifp ifx iif iii iip iix ikf iki ikk ikx ipf ipi ipp ipx ixi kff kfi kfx kif kii kik kip kix kki kkk kkp kpf kpi kpk kpp p-p pff pfi pfk pfp pfx pif pii pik pip pix pkf pki pkp ppf ppi ppk ppp ppx pxk xfx xii xix xpf xpp xxi xxp xxx