a-a a-b a-i aaa aab aag aai aas ab- aba abb abg abi abs ag- aga agb agg agi ags ai- aia aib aig aii ais as- asa asb asg asi ass baa bab bag bai bas bba bbb bbg bbi bbs bga bgb bgg bgi bgs bi- bia bib big bii bis bsa bsb bsg bsi bss gaa gab gag gai gas gba gbg gbi gbs gga ggb ggg ggi ggs gia gib gig gii gis gsa gsb gsg gsi gss ia- iaa iab iag iai ias iba ibb ibg ibi ibs iga igb igg igi igs iia iib iii iis is- isa isb isg isi iss saa sab sag sai sas sba sbb sbg sbi sbs sga sgb sgg sgi sgs sia sib sig sii sis ss- ssa ssb ssg ssi sss