a-a a-b a-c a-z aaa aab aac aao aar aaz ab- aba abb abc abo abr abz ac- aca acb acc aco acr acz aoa aob aoc aoo aor ar- ara arb arc aro arr arz az- aza azb azo azz baa bab bac bao bar baz bba bbb bbc bbo bbr bca bcb bcc bco bcr bcz boa bob boc boo bor boz bra brb bro brr brz bza bzo bzr bzz c-- caa cab cac cao car caz cba cbb cbc cbo cbr cbz cca ccb ccc cco ccr ccz co- coa cob coc coo cor coz cra crb crc cro crr crz cz- czc czo oaa oab oac oao oar ob- oba obb obc obo obr oc- oca ocb occ oco ocr ocz oo- ooa oob ooc ooo oor or- ora orb orc oro orr orz oza ozo ozz ra- raa rab rac rao rar raz rba rbb rbc rbo rbr rca rcb rcc rco rcr roa rob roc roo ror roz rra rrb rrc rrr rza rzb rzo zaa zab zac zao zar zaz zbb zbc zbr zco zo- zoa zob zoc zoo zor zro zzr zzz