-ol bbb bbf bbl bbo bbs bfb bff bfl bfo bfs blb blf bll blo bls bob bof bol boo bos bsb bsf bsl bso bss fbb fbf fbl fbo fbs fff ffl ffo ffs flb flf fll flo fls fob fof fol foo fos fsb fsf fsl fso fss lbb lbf lbl lbo lbs lfb lff lfl lfo lfs llb llf lll llo lls lob lof lol loo los lsb lsf lsl lso lss ob- obb obf obl obo obs of- ofb off ofl ofo ofs olb olf oll olo ols oo- oob oof ool ooo oos os- osb osf osl oso oss sbb sbf sbl sbo sbs sfb sff sfl sfo sfs slb slf sll slo sls sob sof sol soo sos ss- ssb ssf ssl sso sss