fff ffi ffo ffp ffs fft ffx fif fii fip fis fit fix fof foi foo fop fos fot fox fpi fpo fpp fps fpt fpx fsf fsi fso fsp fss fst fsx ftf fti fto ftp fts ftt ftx fxi fxp fxs fxt fxx i-f iff ifi ifo ifp ifs ift ifx iif iii iio iip iis iit iix io- iof ioi ioo iop ios iot ipf ipi ipo ipp ips ipt ipx is- isf isi iso isp iss ist itf iti ito itp its itt itx ixi o-i of- off ofi ofo ofp ofs oft ofx oif oii oio oip ois oit oo- oof ooi ooo oop oos oot oox op- opf opi opo opp ops opt opx os- osf osi oso osp oss ost osx ot- otf oti oto otp ots ott ox- oxf oxi oxo oxt oxx p-p pff pfi pfo pfp pfs pft pfx pif pii pio pip pis pit pix pof poi poo pop pos pot pox ppf ppi ppo ppp pps ppt ppx ps- psf psi pso psp pss pst psx pt- ptf pti pto ptp pts ptt ptx pxs pxt sff sfi sfo sfp sfs sft sfx sif sii sio sip sis sit six sof soi soo sop sos sot sox spf spi spo spp sps spt spx ss- ssf ssi sso ssp sss sst ssx stf sti sto stp sts stt stx sxi sxs sxt t-x tff tfi tfo tfp tfs tft tfx tif tii tio tip tis tit tix to- tof toi too top tos tot tox tpf tpi tpo tpp tps tpt tpx tsf tsi tso tsp tss tst tsx ttf tti tto ttp tts ttt ttx txf txi txs txt xfs xft xfx xii xio xis xit xix xof xoi xoo xop xos xot xox xpf xpo xpp xps xpt xsi xsp xss xst xtf xti xtp xts xtx xxi xxo xxp xxx