a-a a-c a-t aaa aac aar aas aat ac- aca acc acr acs act ar- ara arc arr ars art as- asa asc asr ass ast at- ata atc atr ats att c-- caa cac car cas cat cca ccc ccr ccs cct cra crc crr crs crt csa csc csr css cst cta ctc ctr cts ctt ra- raa rac rar ras rat rca rcc rcr rcs rct rra rrc rrr rrs rrt rsa rsc rsr rss rst rta rtc rtr rts rtt saa sac sar sas sat sca scc scr scs sct sr- sra src srr srs srt ss- ssa ssc ssr sss sst sta stc str sts stt taa tac tar tas tat tca tcc tcr tcs tct tra trc trr trs trt tsa tsc tsr tss tst tta ttc ttr tts ttt