a-a a-b aaa aab aag aao aas ab- aba abb abg abo abs ag- aga agb agg ago ags aoa aob aog aoo aos as- asa asb asg aso ass baa bab bag bao bas bba bbb bbg bbo bbs bga bgb bgg bgo bgs boa bob bog boo bos bsa bsb bsg bso bss gaa gab gag gao gas gba gbg gbo gbs gga ggb ggg ggo ggs goa gob gog goo gos gsa gsb gsg gso gss oaa oab oag oao oas ob- oba obb obg obo obs oga ogg ogo ogs oo- ooa oob oog ooo oos os- osa osb osg oso oss saa sab sag sao sas sba sbb sbg sbo sbs sga sgb sgg sgo sgs soa sob sog soo sos ss- ssa ssb ssg sso sss