-ol bbb bbl bbo bbs bbt blb bll blo bls blt bob bol boo bos bot bsb bsl bso bss bst btb btl bto bts btt lbb lbl lbo lbs lbt llb lll llo lls llt lob lol loo los lot lsb lsl lso lss lst ltb ltl lto lts ltt ob- obb obl obo obs obt olb oll olo ols olt oo- oob ool ooo oos oot os- osb osl oso oss ost ot- otb otl oto ots ott sbb sbl sbo sbs sbt slb sll slo sls slt sob sol soo sos sot ss- ssb ssl sso sss sst stb stl sto sts stt tbb tbl tbo tbs tbt tll tlo tls tlt to- tob tol too tos tot tsb tsl tso tss tst ttb ttl tto tts ttt