a-a a-b a-c a-t a-z aaa aab aac aak aar aat aaz ab- aba abb abc abk abr abt abz ac- aca acb acc ack acr act acz aka akb akc akk akr ar- ara arb arc ark arr art arz at- ata atb atc atr att atz az- aza azb azt azz baa bab bac bak bar bat baz bba bbb bbc bbk bbr bbt bca bcb bcc bck bcr bct bcz bka bkb bkc bkk bkr bkt bra brb brk brr brt brz bta btb btc btk btr btt btz bza bzr bzz c-- caa cab cac cak car cat caz cba cbb cbc cbk cbr cbt cbz cca ccb ccc cck ccr cct ccz cka ckb ckc ckt cra crb crc crk crr crt crz cta ctb ctc ctk ctr ctt ctz cz- czc czk czt k-t k-z ka- kaa kab kac kak kar kat kaz kba kbb kbc kbk kbr kbz 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 raz rba rbb rbc rbk rbr rbt rca rcb rcc rcr rct rkb rkc rkk rkt rkz rra rrb rrc rrk rrr rrt rta rtb rtc rtk rtr rtt rtz rza rzb taa tab tac tak tar tat taz tba tbb tbc tbk tbr tbt tbz tca tcb tcc tck tcr tct tka tkb tkc tkk tkr tkt tkz tra trb trc trk trr trt trz tta ttb ttc ttk ttr ttt tza zaa zab zac zak zar zat zaz zbb zbc zbr zbt zka zta ztr zzr zzt zzz