a-a a-c aaa aac aao aar aas aax ac- aca acc aco acr acs acx aoa aoc aoo aor aos aox ar- ara arc aro arr ars arx as- asa asc aso asr ass asx ax- axa axo axr axs axx c-- caa cac cao car cas cax cca ccc cco ccr ccs ccx co- coa coc coo cor cos cox cra crc cro crr crs crx csa csc cso csr css csx cxc cxo cxr cxs cxx oaa oac oao oar oas oax oc- oca occ oco ocr ocs ocx oo- ooa ooc ooo oor oos oox or- ora orc oro orr ors orx os- osa osc oso osr oss osx ox- oxa oxc oxo oxx ra- raa rac rao rar ras rax rca rcc rco rcr rcs rcx roa roc roo ror ros rox rra rrc rrr rrs rsa rsc rso rsr rss rsx rxr rxs saa sac sao sar sas sax sca scc sco scr scs scx soa soc soo sor sos sox sr- sra src sro srr srs srx ss- ssa ssc sso ssr sss ssx sxc sxs xaa xac xar xas xcr xcx xoa xoc xoo xor xos xox xrc xrx xsa xsc xss xxo xxx