bbb bbe bbk bbo bbs be- beb bee bek beo bes bkb bke bkk bko bks bob boe bok boo bos bsb bse bsk bso bss ebb ebe ebk ebo ebs eeb eee eek eeo ees ekb eke eko eks eo- eob eoe eok eoo eos es- esb ese esk eso ess kbb kbe kbk kbo kbs ke- keb kee kek keo kes kkb kke kkk kks kob koe kok koo kos ksb kse ksk kso kss ob- obb obe obk obo obs oeb oee oeo oes okb oke okk oko oks oo- oob ook ooo oos os- osb ose osk oso oss sbb sbe sbk sbo sbs se- seb see sek seo ses sk- skb ske skk sko sks sob soe sok soo sos ss- ssb sse ssk sso sss