-ol bbb bbc bbk bbl bbo bbs bcb bcc bck bcl bco bcs bkb bkc bkk bkl bko bks blb blc blk bll blo bls bob boc bok bol boo bos bsb bsc bsk bsl bso bss c-- cbb cbc cbk cbl cbo cbs ccb ccc cck ccl cco ccs ckb ckc cko cks cl- clb clc clk cll clo cls co- cob coc cok col coo cos csb csc csk csl cso css kbb kbc kbk kbl kbo kbs kcb kcc kck kcl kcs kkb kkc kkk kkl kks kl- klb klc klo kls kob koc kok kol koo kos ksb ksc ksk ksl kso kss lbb lbc lbk lbl lbo lbs lcb lcc lck lcl lco lcs lkb lkl lks llb llc llk lll llo lls lob loc lok lol loo los lsb lsc lsk lsl lso lss ob- obb obc obk obl obo obs oc- ocb occ ock ocl oco ocs okb okc okk okl oko oks olb olc olk oll olo ols oo- oob ooc ook ool ooo oos os- osb osc osk osl oso oss sbb sbc sbk sbl sbo sbs scb scc sck scl sco scs sk- skb skc skk skl sko sks slb slc slk sll slo sls sob soc sok sol soo sos ss- ssb ssc ssk ssl sso sss