a-a a-b a-c a-z aaa aab aac aao aas aaz ab- aba abb abc abo abs abz ac- aca acb acc aco acs acz aoa aob aoc aoo aos as- asa asb asc aso ass asz az- aza azb azo azs azz baa bab bac bao bas baz bba bbb bbc bbo bbs bca bcb bcc bco bcs bcz boa bob boc boo bos boz bsa bsb bsc bso bss bza bzo bzs bzz c-- caa cab cac cao cas caz cba cbb cbc cbo cbs cbz cca ccb ccc cco ccs ccz co- coa cob coc coo cos coz csa csb csc cso css csz cz- czc czo oaa oab oac oao oas ob- oba obb obc obo obs oc- oca ocb occ oco ocs ocz oo- ooa oob ooc ooo oos os- osa osb osc oso oss oza ozo ozs ozz saa sab sac sao sas saz sba sbb sbc sbo sbs sca scb scc sco scs soa sob soc soo sos soz ss- ssa ssb ssc sso sss ssz sza zaa zab zac zao zas zaz zbb zbc zbs zco zcs zo- zoa zob zoc zoo zos zsa zsz zzs zzz