bbb bbf bbo bbs bbt bbx bfb bff bfo bfs bft bfx bob bof boo bos bot box bsb bsf bso bss bst bsx btb btf bto bts btt btx bxb bxo bxx fbb fbf fbo fbs fbt fbx fff ffo ffs fft ffx fob fof foo fos fot fox fsb fsf fso fss fst fsx ftb ftf fto fts ftt ftx fxs fxt fxx ob- obb obf obo obs obt obx of- ofb off ofo ofs oft ofx oo- oob oof ooo oos oot oox os- osb osf oso oss ost osx ot- otb otf oto ots ott ox- oxb oxf oxo oxt oxx sbb sbf sbo sbs sbt sbx sfb sff sfo sfs sft sfx sob sof soo sos sot sox ss- ssb ssf sso sss sst ssx stb stf sto sts stt stx sxs sxt t-x tbb tbf tbo tbs tbt tfb tff tfo tfs tft tfx to- tob tof too tos tot tox tsb tsf tso tss tst tsx ttb ttf tto tts ttt ttx txf txs txt xbx xfs xft xfx xof xoo xos xot xox xsb xss xst xtf xts xtx xxo xxx