a-a a-b a-c a-t a-z aaa aab aac aao aar aat aaz ab- aba abb abc abo abr abt abz ac- aca acb acc aco acr act acz aoa aob aoc aoo aor aot ar- ara arb arc aro arr art arz at- ata atb atc ato atr att atz az- aza azb azo azt azz baa bab bac bao bar bat baz bba bbb bbc bbo bbr bbt bca bcb bcc bco bcr bct bcz boa bob boc boo bor bot boz bra brb bro brr brt brz bta btb btc bto btr btt btz bza bzo bzr bzz c-- caa cab cac cao car cat caz cba cbb cbc cbo cbr cbt cbz cca ccb ccc cco ccr cct ccz co- coa cob coc coo cor cot coz cra crb crc cro crr crt crz cta ctb ctc cto ctr ctt ctz cz- czc czo czt oaa oab oac oao oar oat ob- oba obb obc obo obr obt oc- oca ocb occ oco ocr oct ocz oo- ooa oob ooc ooo oor oot or- ora orb orc oro orr ort orz ot- ota otb otc oto otr ott otz oza ozo ozt ozz ra- raa rab rac rao rar rat raz rba rbb rbc rbo rbr rbt rca rcb rcc rco rcr rct roa rob roc roo ror rot roz rra rrb rrc rrr rrt rta rtb rtc rto rtr rtt rtz rza rzb rzo taa tab tac tao tar tat taz tba tbb tbc tbo tbr tbt tbz tca tcb tcc tco tcr tct to- toa tob toc too tor tot toz tra trb trc tro trr trt trz tta ttb ttc tto ttr ttt tza zaa zab zac zao zar zat zaz zbb zbc zbr zbt zco zo- zoa zob zoc zoo zor zot zro zta ztr zzr zzt zzz