a-a aaa aaf aap aas aax af- afa aff afp afs afx ap- apa apf app aps apx as- asa asf asp ass asx ax- axa axp axs axx faa faf fap fas fax ffa fff ffp ffs ffx fpa fpp fps fpx fsa fsf fsp fss fsx fxp fxs fxx p-p paa paf pap pas pax pfa pff pfp pfs pfx ppa ppf ppp pps ppx ps- psa psf psp pss psx pxs saa saf sap sas sax sfa sff sfp sfs sfx spa spf spp sps spx ss- ssa ssf ssp sss ssx sxs xaa xaf xap xas xfa xfs xfx xpa xpf xpp xps xsa xsp xss xxp xxx