-ol fff ffl ffo ffs fft flf fll flo fls flt fof fol foo fos fot fsf fsl fso fss fst ftf ftl fto fts ftt lff lfl lfo lfs lft llf lll llo lls llt lof lol loo los lot lsf lsl lso lss lst ltf ltl lto lts ltt of- off ofl ofo ofs oft olf oll olo ols olt oo- oof ool ooo oos oot os- osf osl oso oss ost ot- otf otl oto ots ott sff sfl sfo sfs sft slf sll slo sls slt sof sol soo sos sot ss- ssf ssl sso sss sst stf stl sto sts stt tff tfl tfo tfs tft tlf tll tlo tls tlt to- tof tol too tos tot tsf tsl tso tss tst ttf ttl tto tts ttt