a-a a-c aaa aac aak aao aar aas ac- aca acc ack aco acr acs aka akc akk ako akr aks aoa aoc aok aoo aor aos ar- ara arc ark aro arr ars as- asa asc ask aso asr ass c-- caa cac cak cao car cas cca ccc cck cco ccr ccs cka ckc cko cks co- coa coc cok coo cor cos cra crc crk cro crr crs csa csc csk cso csr css ka- kaa kac kak kao kar kas kca kcc kck kcr kcs kkc kkk kkr kks koa koc kok koo kor kos kra krc krk kro krr krs ksa ksc ksk kso ksr kss oaa oac oak oao oar oas oc- oca occ ock oco ocr ocs oka okc okk oko okr oks oo- ooa ooc ook ooo oor oos or- ora orc ork oro orr ors os- osa osc osk oso osr oss ra- raa rac rak rao rar ras rca rcc rco rcr rcs rkc rkk rko rks roa roc rok roo ror ros rra rrc rrk rrr rrs rsa rsc rsk rso rsr rss saa sac sak sao sar sas sca scc sck sco scr scs sk- ska skc skk sko skr sks soa soc sok soo sor sos sr- sra src srk sro srr srs ss- ssa ssc ssk sso ssr sss