-ol bbb bbc bbk bbl bbo bbt bcb bcc bck bcl bco bct bkb bkc bkk bkl bko bkt blb blc blk bll blo blt bob boc bok bol boo bot btb btc btk btl bto btt c-- cbb cbc cbk cbl cbo cbt ccb ccc cck ccl cco cct ckb ckc cko ckt cl- clb clc clk cll clo clt co- cob coc cok col coo cot ctb ctc ctk ctl cto ctt k-t kbb kbc kbk kbl kbo kcb kcc kck kcl kct kkb kkc kkk kkl kkt kl- klb klc klo klt kob koc kok kol koo kot ktb ktc ktk ktl kto ktt lbb lbc lbk lbl lbo lbt lcb lcc lck lcl lco lct lkb lkl lkt llb llc llk lll llo llt lob loc lok lol loo lot ltb ltc ltk ltl lto ltt ob- obb obc obk obl obo obt oc- ocb occ ock ocl oco oct okb okc okk okl oko olb olc olk oll olo olt oo- oob ooc ook ool ooo oot ot- otb otc otk otl oto ott tbb tbc tbk tbl tbo tbt tcb tcc tck tcl tco tct tkb tkc tkk tkl tko tkt tlc tlk tll tlo tlt to- tob toc tok tol too tot ttb ttc ttk ttl tto ttt