-er bbb bbc bbe bbg bbk bbn bbo bbr bcb bcc bce bcg bck bcn bco bcr be- beb bec bee beg bek ben beo ber bgb bgc bge bgg bgk bgn bgo bgr bkb bkc bke bkg bkk bkn bko bkr bnb bnc bne bng bnk bnn bno bnr bob boc boe bog bok bon boo bor brb bre brg brk brn bro brr c-- cbb cbc cbe cbg cbk cbn cbo cbr ccb ccc cce ccg cck ccn cco ccr ce- ceb cec cee ceg cek cen ceo cer cgb cgc cge cgg cgn cgo cgr ckb ckc cko cn- cnb cnc cne cng cnn cno cnr co- cob coc coe cog cok con coo cor crb crc cre crg crk crn cro crr ebb ebc ebe ebg ebk ebn ebo ebr ec- ecb ecc ece ecg eck ecn eco ecr eeb eec eee eeg eek een eeo eer egb egc ege egg egn ego egr ekb ekc eke ekg eko ekr en- enb enc ene eng enk enn eno enr eo- eob eoc eoe eog eok eon eoo eor erb erc ere erg erk ern ero err gbc gbe gbg gbk gbn gbo gbr gcb gcc gce gcg gck gcn gco gcr ge- geb gec gee geg gek gen geo ger ggb ggc ggg ggn ggo ggr gkb gkn gko gnb gnc gne gnn gno gnr gob goc goe gog gok gon goo gor grb grc gre grg grk grn gro grr kbb kbc kbe kbk kbn kbo kbr kcb kcc kce kcg kck kcn kcr ke- keb kec kee keg kek ken keo ker kgb kgc kgo kkb kkc kke kkk kkn kkr kn- knc kne kng knk knn kno knr kob koc koe kog kok kon koo kor krc krg krk krn kro krr nbb nbc nbe nbg nbk nbn nbo nbr ncb ncc nce ncg nck ncn nco ncr ne- neb nec nee neg nek nen neo ner ngb ngc nge ngg ngk ngn ngo nkc nke nkk nkn nko nkr nnb nnc nne nng nnk nnn nno no- nob noc noe nog nok non noo nor nrb nrc nre nrg nrk nrn nro nrr ob- obb obc obe obg obk obn obo obr oc- ocb occ ocg ock ocn oco ocr oeb oec oee oeg oen oeo oer ogc oge ogg ogn ogo okb okc oke okg okk oko okr on- onb onc one ong onk onn ono onr oo- oob ooc oog ook oon ooo oor or- orb orc ore org ork orn oro orr rbb rbc rbe rbg rbk rbn rbo rbr rcb rcc rce rcg rcn rco rcr re- reb rec ree reg rek ren reo rer rgb rgc rge rgg rgk rgn rgo rgr rkb rkc rke rkg rkk rko rnb rnc rng rnn rno rnr rob roc roe rog rok ron roo ror rrb rrc rrg rrk rrn rrr