-ol bbb bbc bbe bbk bbl bbo bbt bcb bcc bce bck bcl bco bct be- beb bec bee bek bel beo bet bkb bkc bke bkk bkl bko bkt blb blc ble blk bll blo blt bob boc boe bok bol boo bot btb btc bte btk btl bto btt c-- cbb cbc cbe cbk cbl cbo cbt ccb ccc cce cck ccl cco cct ce- ceb cec cee cek cel ceo cet ckb ckc cko ckt cl- clb clc cle clk cll clo clt co- cob coc coe cok col coo cot ctb ctc cte ctk ctl cto ctt ebb ebc ebe ebk ebl ebo ebt ec- ecb ecc ece eck ecl eco ect eeb eec eee eek eel eeo eet ekb ekc eke ekl eko ekt elb elc ele elk ell elo elt eo- eob eoc eoe eok eol eoo eot etb etc ete etk etl eto ett k-t kbb kbc kbe kbk kbl kbo kcb kcc kce kck kcl kct ke- keb kec kee kek kel keo ket kkb kkc kke kkk kkl kkt kl- klb klc klo klt kob koc koe kok kol koo kot ktb ktc kte ktk ktl kto ktt lbb lbc lbe lbk lbl lbo lbt lcb lcc lce lck lcl lco lct leb lec lee lek lel leo let lkb lkl lkt llb llc lle llk lll llo llt lob loc loe lok lol loo lot ltb ltc lte ltk ltl lto ltt ob- obb obc obe obk obl obo obt oc- ocb occ ock ocl oco oct oeb oec oee oel oeo oet okb okc oke okk okl oko olb olc ole olk oll olo olt oo- oob ooc ook ool ooo oot ot- otb otc ote otk otl oto ott tbb tbc tbe tbk tbl tbo tbt tcb tcc tce tck tcl tco tct te- teb tec tee tek tel teo tet tkb tkc tke tkk tkl tko tkt tlc tle tlk tll tlo tlt to- tob toc toe tok tol too tot ttb ttc tte ttk ttl tto ttt