bbb bbc bbe bbk bbo bbs bcb bcc bce bck bco bcs be- beb bec bee bek beo bes bkb bkc bke bkk bko bks bob boc boe bok boo bos bsb bsc bse bsk bso bss c-- cbb cbc cbe cbk cbo cbs ccb ccc cce cck cco ccs ce- ceb cec cee cek ceo ces ckb ckc cko cks co- cob coc coe cok coo cos csb csc cse csk cso css ebb ebc ebe ebk ebo ebs ec- ecb ecc ece eck eco ecs eeb eec eee eek eeo ees ekb ekc eke eko eks eo- eob eoc eoe eok eoo eos es- esb esc ese esk eso ess kbb kbc kbe kbk kbo kbs kcb kcc kce kck kcs ke- keb kec kee kek keo kes kkb kkc kke kkk kks kob koc koe kok koo kos ksb ksc kse ksk kso kss ob- obb obc obe obk obo obs oc- ocb occ ock oco ocs oeb oec oee oeo oes okb okc oke okk oko oks oo- oob ooc ook ooo oos os- osb osc ose osk oso oss sbb sbc sbe sbk sbo sbs scb scc sce sck sco scs se- seb sec see sek seo ses sk- skb skc ske skk sko sks sob soc soe sok soo sos ss- ssb ssc sse ssk sso sss