a-a aaa aaf aar aas aax af- afa aff afr afs afx ar- ara arf arr ars arx as- asa asf asr ass asx ax- axa axr axs axx faa faf far fas fax ffa fff ffr ffs ffx fra frf frr frs fsa fsf fsr fss fsx fxr fxs fxx ra- raa raf rar ras rax rfa rff rfr rfs rra rrf rrr rrs rsa rsf rsr rss rsx rxr rxs saa saf sar sas sax sfa sff sfr sfs sfx sr- sra srf srr srs srx ss- ssa ssf ssr sss ssx sxs xaa xaf xar xas xfa xfs xfx xrf xrx xsa xss xxx