bbb bbc bbe bbk bbn bbo bcb bcc bce bck bcn bco be- beb bec bee bek ben beo bkb bkc bke bkk bkn bko bnb bnc bne bnk bnn bno bob boc boe bok bon boo c-- cbb cbc cbe cbk cbn cbo ccb ccc cce cck ccn cco ce- ceb cec cee cek cen ceo ckb ckc cko cn- cnb cnc cne cnn cno co- cob coc coe cok con coo ebb ebc ebe ebk ebn ebo ec- ecb ecc ece eck ecn eco eeb eec eee eek een eeo ekb ekc eke eko en- enb enc ene enk enn eno eo- eob eoc eoe eok eon eoo kbb kbc kbe kbk kbn kbo kcb kcc kce kck kcn ke- keb kec kee kek ken keo kkb kkc kke kkk kkn kn- knc kne knk knn kno kob koc koe kok kon koo nbb nbc nbe nbk nbn nbo ncb ncc nce nck ncn nco ne- neb nec nee nek nen neo nkc nke nkk nkn nko nnb nnc nne nnk nnn nno no- nob noc noe nok non noo ob- obb obc obe obk obn obo oc- ocb occ ock ocn oco oeb oec oee oen oeo okb okc oke okk oko on- onb onc one onk onn ono oo- oob ooc ook oon ooo