-ol bbb bbc bbe bbk bbl bbo bcb bcc bce bck bcl bco be- beb bec bee bek bel beo bkb bkc bke bkk bkl bko blb blc ble blk bll blo bob boc boe bok bol boo c-- cbb cbc cbe cbk cbl cbo ccb ccc cce cck ccl cco ce- ceb cec cee cek cel ceo ckb ckc cko cl- clb clc cle clk cll clo co- cob coc coe cok col coo ebb ebc ebe ebk ebl ebo ec- ecb ecc ece eck ecl eco eeb eec eee eek eel eeo ekb ekc eke ekl eko elb elc ele elk ell elo eo- eob eoc eoe eok eol eoo kbb kbc kbe kbk kbl kbo kcb kcc kce kck kcl ke- keb kec kee kek kel keo kkb kkc kke kkk kkl kl- klb klc klo kob koc koe kok kol koo lbb lbc lbe lbk lbl lbo lcb lcc lce lck lcl lco leb lec lee lek lel leo lkb lkl llb llc lle llk lll llo lob loc loe lok lol loo ob- obb obc obe obk obl obo oc- ocb occ ock ocl oco oeb oec oee oel oeo okb okc oke okk okl oko olb olc ole olk oll olo oo- oob ooc ook ool ooo