-er bbb bbc bbe bbk bbo bbr bcb bcc bce bck bco bcr bcz be- beb bec bee bek beo ber bez bkb bkc bke bkk bko bkr bob boc boe bok boo bor boz brb bre brk bro brr brz bze bzo bzr bzz c-- cbb cbc cbe cbk cbo cbr cbz ccb ccc cce cck cco ccr ccz ce- ceb cec cee cek ceo cer cez ckb ckc cko co- cob coc coe cok coo cor coz crb crc cre crk cro crr crz cz- czc cze czk czo ebb ebc ebe ebk ebo ebr ec- ecb ecc ece eck eco ecr eeb eec eee eek eeo eer ekb ekc eke eko ekr eo- eob eoc eoe eok eoo eor erb erc ere erk ero err erz eze ezo ezr ezz k-z kbb kbc kbe kbk kbo kbr kbz kcb kcc kce kck kcr ke- keb kec kee kek keo ker kez kkb kkc kke kkk kkr kob koc koe kok koo kor koz krc krk kro krr kzo ob- obb obc obe obk obo obr oc- ocb occ ock oco ocr ocz oeb oec oee oeo oer okb okc oke okk oko okr oo- oob ooc ook ooo oor or- orb orc ore ork oro orr orz oze ozo ozz rbb rbc rbe rbk rbo rbr rcb rcc rce rco rcr re- reb rec ree rek reo rer rez rkb rkc rke rkk rko rkz rob roc roe rok roo ror roz rrb rrc rrk rrr rzb rze rzo zbb zbc zbr zce zco zeb zec zee zek zeo zer zez zo- zob zoc zoe zok zoo zor zro zzr zzz