-ol bbb bbc bbk bbl bbo bcb bcc bck bcl bco bkb bkc bkk bkl bko blb blc blk bll blo bob boc bok bol boo c-- cbb cbc cbk cbl cbo ccb ccc cck ccl cco ckb ckc cko cl- clb clc clk cll clo co- cob coc cok col coo kbb kbc kbk kbl kbo kcb kcc kck kcl kkb kkc kkk kkl kl- klb klc klo kob koc kok kol koo lbb lbc lbk lbl lbo lcb lcc lck lcl lco lkb lkl llb llc llk lll llo lob loc lok lol loo ob- obb obc obk obl obo oc- ocb occ ock ocl oco okb okc okk okl oko olb olc olk oll olo oo- oob ooc ook ool ooo