a-a a-c a-t aaa aac aar aat aax ac- aca acc acr act acx ar- ara arc arr art arx at- ata atc atr att atx ax- axa axr axt axx c-- caa cac car cat cax cca ccc ccr cct ccx cra crc crr crt crx cta ctc ctr ctt ctx cxc cxr cxt cxx ra- raa rac rar rat rax rca rcc rcr rct rcx rra rrc rrr rrt rta rtc rtr rtt rtx rxr t-x taa tac tar tat tax tca tcc tcr tct tcx tra trc trr trt trx tta ttc ttr ttt ttx txt xaa xac xar xat xcr xcx xrc xrt xrx xtc xtr xtx xxx