-ol bbb bbd bbl bbo bbt bdb bdd bdl bdo bdt blb bld bll blo blt bob bod bol boo bot btb btd btl bto btt dbb dbd dbl dbo dbt ddb ddd ddl ddo ddt dl- dlb dld dll dlo dlt dob dod dol doo dot dtb dtd dtl dto dtt lbb lbd lbl lbo lbt ldb ldd ldl ldo ldt llb lld lll llo llt lob lod lol loo lot ltb ltd ltl lto ltt ob- obb obd obl obo obt odb odd odl odo odt olb old oll olo olt oo- oob ood ool ooo oot ot- otb otd otl oto ott tbb tbd tbl tbo tbt tdb tdd tdl tdo tdt tld tll tlo tlt to- tob tod tol too tot ttb ttd ttl tto ttt