-ol bbb bbl bbo bbr bbs bbt blb bll blo blr bls blt bob bol boo bor bos bot brb brl bro brr brs brt bsb bsl bso bsr bss bst btb btl bto btr bts btt lbb lbl lbo lbr lbs lbt llb lll llo llr lls llt lob lol loo lor los lot lrb lro lrr lrs lrt lsb lsl lso lsr lss lst ltb ltl lto ltr lts ltt ob- obb obl obo obr obs obt olb oll olo ols olt oo- oob ool ooo oor oos oot or- orb orl oro orr ors ort os- osb osl oso osr oss ost ot- otb otl oto otr ots ott rbb rbl rbo rbr rbs rbt rll rlo rlr rls rlt rob rol roo ror ros rot rrb rrl rrr rrs rrt rsb rsl rso rsr rss rst rtb rtl rto rtr rts rtt sbb sbl sbo sbr sbs sbt slb sll slo slr sls slt sob sol soo sor sos sot sr- srb srl sro srr srs srt ss- ssb ssl sso ssr sss sst stb stl sto str sts stt tbb tbl tbo tbr tbs tbt tll tlo tlr tls tlt to- tob tol too tor tos tot trb trl tro trr trs trt tsb tsl tso tsr tss tst ttb ttl tto ttr tts ttt