a-a a-t aaa aaf aag aas aat af- afa aff afg afs aft ag- aga agf agg ags agt as- asa asf asg ass ast at- ata atf atg ats att faa faf fag fas fat ffa fff ffg ffs fft fga fgf fgg fgs fgt fsa fsf fsg fss fst fta ftf ftg fts ftt gaa gaf gag gas gat gfa gff gfs gft gga ggg ggs ggt gsa gsf gsg gss gst gta gtf gtg gts gtt saa saf sag sas sat sfa sff sfg sfs sft sga sgf sgg sgs sgt ss- ssa ssf ssg sss sst sta stf stg sts stt taa taf tag tas tat tfa tff tfg tfs tft tga tgf tgg tgs tgt tsa tsf tsg tss tst tta ttf ttg tts ttt