ddd ddf ddo dds ddt dfd dff dfo dfs dft dod dof doo dos dot dsd dsf dso dss dst dtd dtf dto dts dtt fdd fdf fdo fds fdt ffd fff ffo ffs fft fof foo fos fot fsd fsf fso fss fst ftd ftf fto fts ftt odd odf odo ods odt of- ofd off ofo ofs oft oo- ood oof ooo oos oot os- osd osf oso oss ost ot- otd otf oto ots ott sdd sdf sdo sds sdt sfd sff sfo sfs sft sod sof soo sos sot ss- ssd ssf sso sss sst std stf sto sts stt tdd tdf tdo tds tdt tfd tff tfo tfs tft to- tod tof too tos tot tsd tsf tso tss tst ttd ttf tto tts ttt