a-a a-b a-c a-t aaa aab aac aak aar aat ab- aba abb abc abk abr abt ac- aca acb acc ack acr act aka akb akc akk akr ar- ara arb arc ark arr art at- ata atb atc atr att baa bab bac bak bar bat bba bbb bbc bbk bbr bbt bca bcb bcc bck bcr bct bka bkb bkc bkk bkr bkt bra brb brk brr brt bta btb btc btk btr btt c-- caa cab cac cak car cat cba cbb cbc cbk cbr cbt cca ccb ccc cck ccr cct cka ckb ckc ckt cra crb crc crk crr crt cta ctb ctc ctk ctr ctt k-t ka- kaa kab kac kak kar kat kba kbb kbc kbk kbr kca kcb kcc kck kcr kct kkb kkc kkk kkr kkt kra krc krk krr krt kta ktb ktc ktk ktr ktt ra- raa rab rac rak rar rat rba rbb rbc rbk rbr rbt rca rcb rcc rcr rct rkb rkc rkk rkt rra rrb rrc rrk rrr rrt rta rtb rtc rtk rtr rtt taa tab tac tak tar tat tba tbb tbc tbk tbr tbt tca tcb tcc tck tcr tct tka tkb tkc tkk tkr tkt tra trb trc trk trr trt tta ttb ttc ttk ttr ttt