-er bbb bbc bbe bbn bbo bbr bcb bcc bce bcn bco bcr be- beb bec bee ben beo ber bnb bnc bne bnn bno bnr bob boc boe bon boo bor brb bre brn bro brr c-- cbb cbc cbe cbn cbo cbr ccb ccc cce ccn cco ccr ce- ceb cec cee cen ceo cer cn- cnb cnc cne cnn cno cnr co- cob coc coe con coo cor crb crc cre crn cro crr ebb ebc ebe ebn ebo ebr ec- ecb ecc ece ecn eco ecr eeb eec eee een eeo eer en- enb enc ene enn eno enr eo- eob eoc eoe eon eoo eor erb erc ere ern ero err nbb nbc nbe nbn nbo nbr ncb ncc nce ncn nco ncr ne- neb nec nee nen neo ner nnb nnc nne nnn nno no- nob noc noe non noo nor nrb nrc nre nrn nro nrr ob- obb obc obe obn obo obr oc- ocb occ ocn oco ocr oeb oec oee oen oeo oer on- onb onc one onn ono onr oo- oob ooc oon ooo oor or- orb orc ore orn oro orr rbb rbc rbe rbn rbo rbr rcb rcc rce rcn rco rcr re- reb rec ree ren reo rer rnb rnc rnn rno rnr rob roc roe ron roo ror rrb rrc rrn rrr