a-a a-t aaa aaf aao aas aat af- afa aff afo afs aft aoa aof aoo aos aot as- asa asf aso ass ast at- ata atf ato ats att faa faf fao fas fat ffa fff ffo ffs fft foa fof foo fos fot fsa fsf fso fss fst fta ftf fto fts ftt oaa oaf oao oas oat of- ofa off ofo ofs oft oo- ooa oof ooo oos oot os- osa osf oso oss ost ot- ota otf oto ots ott saa saf sao sas sat sfa sff sfo sfs sft soa sof soo sos sot ss- ssa ssf sso sss sst sta stf sto sts stt taa taf tao tas tat tfa tff tfo tfs tft to- toa tof too tos tot tsa tsf tso tss tst tta ttf tto tts ttt