a-a a-c aaa aac aao aar aas ac- aca acc aco acr acs aoa aoc aoo aor aos ar- ara arc aro arr ars as- asa asc aso asr ass c-- caa cac cao car cas cca ccc cco ccr ccs co- coa coc coo cor cos cra crc cro crr crs csa csc cso csr css oaa oac oao oar oas oc- oca occ oco ocr ocs oo- ooa ooc ooo oor oos or- ora orc oro orr ors os- osa osc oso osr oss ra- raa rac rao rar ras rca rcc rco rcr rcs roa roc roo ror ros rra rrc rrr rrs rsa rsc rso rsr rss saa sac sao sar sas sca scc sco scr scs soa soc soo sor sos sr- sra src sro srr srs ss- ssa ssc sso ssr sss