bbb bbc bbe bbk bbl bcb bcc bce bck bcl be- beb bec bee bek bel bkb bkc bke bkk bkl blb blc ble blk bll c-- cbb cbc cbe cbk cbl ccb ccc cce cck ccl ce- ceb cec cee cek cel ckb ckc cl- clb clc cle clk cll ebb ebc ebe ebk ebl ec- ecb ecc ece eck ecl eeb eec eee eek eel ekb ekc eke ekl elb elc ele elk ell kbb kbc kbe kbk kbl kcb kcc kce kck kcl ke- keb kec kee kek kel kkb kkc kke kkk kkl kl- klb klc lbb lbc lbe lbk lbl lcb lcc lce lck lcl leb lec lee lek lel lkb lkl llb llc lle llk lll