bbb bbc bbe bbk bbo bcb bcc bce bck bco be- beb bec bee bek beo bkb bkc bke bkk bko bob boc boe bok boo c-- cbb cbc cbe cbk cbo ccb ccc cce cck cco ce- ceb cec cee cek ceo ckb ckc cko co- cob coc coe cok coo ebb ebc ebe ebk ebo ec- ecb ecc ece eck eco eeb eec eee eek eeo ekb ekc eke eko eo- eob eoc eoe eok eoo kbb kbc kbe kbk kbo kcb kcc kce kck ke- keb kec kee kek keo kkb kkc kke kkk kob koc koe kok koo ob- obb obc obe obk obo oc- ocb occ ock oco oeb oec oee oeo okb okc oke okk oko oo- oob ooc ook ooo