a-a a-b a-t a-z aaa aab aao aar aas aat aaz ab- aba abb abo abr abs abt abz aoa aob aoo aor aos aot ar- ara arb aro arr ars art arz as- asa asb aso asr ass ast asz at- ata atb ato atr ats att atz az- aza azb azo azs azt azz baa bab bao bar bas bat baz bba bbb bbo bbr bbs bbt boa bob boo bor bos bot boz bra brb bro brr brs brt brz bsa bsb bso bsr bss bst bta btb bto btr bts btt btz bza bzo bzr bzs bzz oaa oab oao oar oas oat ob- oba obb obo obr obs obt oo- ooa oob ooo oor oos oot or- ora orb oro orr ors ort orz os- osa osb oso osr oss ost ot- ota otb oto otr ots ott otz oza ozo ozs ozt ozz ra- raa rab rao rar ras rat raz rba rbb rbo rbr rbs rbt roa rob roo ror ros rot roz rra rrb rrr rrs rrt rsa rsb rso rsr rss rst rta rtb rto rtr rts rtt rtz rza rzb rzo saa sab sao sar sas sat saz sba sbb sbo sbr sbs sbt soa sob soo sor sos sot soz sr- sra srb sro srr srs srt ss- ssa ssb sso ssr sss sst ssz sta stb sto str sts stt stz sza szr taa tab tao tar tas tat taz tba tbb tbo tbr tbs tbt tbz to- toa tob too tor tos tot toz tra trb tro trr trs trt trz tsa tsb tso tsr tss tst tta ttb tto ttr tts ttt tza tzs zaa zab zao zar zas zat zaz zbb zbr zbs zbt zo- zoa zob zoo zor zos zot zro zrs zsa zst zsz zta ztr zzr zzs zzt zzz