a-a a-c a-t aaa aac aaf aas aat ac- aca acc acf acs act af- afa afc aff afs aft as- asa asc asf ass ast at- ata atc atf ats att c-- caa cac caf cas cat cca ccc ccf ccs cct cfa cfc cff cfs cft csa csc csf css cst cta ctc ctf cts ctt faa fac faf fas fat fca fcc fcf fcs fct ffa ffc fff ffs fft fsa fsc fsf fss fst fta ftc ftf fts ftt saa sac saf sas sat sca scc scf scs sct sfa sfc sff sfs sft ss- ssa ssc ssf sss sst sta stc stf sts stt taa tac taf tas tat tca tcc tcf tcs tct tfa tfc tff tfs tft tsa tsc tsf tss tst tta ttc ttf tts ttt