fff ffo ffr fft ffx fof foo for fot fox frf fro frr frt ftf fto ftr ftt ftx fxr fxt fxx of- off ofo ofr oft ofx oo- oof ooo oor oot oox or- orf oro orr ort orx ot- otf oto otr ott ox- oxf oxo oxt oxx rff rfo rfr rft rof roo ror rot rox rrf rrr rrt rtf rto rtr rtt rtx rxr t-x tff tfo tfr tft tfx to- tof too tor tot tox trf tro trr trt trx ttf tto ttr ttt ttx txf txt xft xfx xof xoo xor xot xox xrf xrt xrx xtf xtr xtx xxo xxx