-er b-u bbb bbc bbe bbk bbn bbo bbr bbu bcb bcc bce bck bcn bco bcr bcu be- beb bec bee bek ben beo ber beu bkb bkc bke bkk bkn bko bkr bnb bnc bne bnk bnn bno bnr bnu bob boc boe bok bon boo bor bou brb bre brk brn bro brr bru bub buc bue buk bun buo bur buu c-- cbb cbc cbe cbk cbn cbo cbr cbu ccb ccc cce cck ccn cco ccr ccu ce- ceb cec cee cek cen ceo cer ceu ckb ckc cko cn- cnb cnc cne cnn cno cnr cnu co- cob coc coe cok con coo cor cou crb crc cre crk crn cro crr cru cub cuc cue cuk cun cuo cur cuu ebb ebc ebe ebk ebn ebo ebr ebu ec- ecb ecc ece eck ecn eco ecr ecu eeb eec eee eek een eeo eer ekb ekc eke eko ekr eku en- enb enc ene enk enn eno enr enu eo- eob eoc eoe eok eon eoo eor eou erb erc ere erk ern ero err eru eu- eub euc eue eun eur kbb kbc kbe kbk kbn kbo kbr kbu kcb kcc kce kck kcn kcr kcu ke- keb kec kee kek ken keo ker kkb kkc kke kkk kkn kkr kku kn- knc kne knk knn kno knr knu kob koc koe kok kon koo kor kou krc krk krn kro krr kru kub kuc kue kuk kun kur kuu nbb nbc nbe nbk nbn nbo nbr nbu ncb ncc nce nck ncn nco ncr ncu ne- neb nec nee nek nen neo ner neu nkc nke nkk nkn nko nkr nku nnb nnc nne nnk nnn nno nnu no- nob noc noe nok non noo nor nou nrb nrc nre nrk nrn nro nrr nru nub nuc nue nuk nun nuo nur nuu ob- obb obc obe obk obn obo obr obu oc- ocb occ ock ocn oco ocr ocu oeb oec oee oen oeo oer okb okc oke okk oko okr oku on- onb onc one onk onn ono onr onu oo- oob ooc ook oon ooo oor or- orb orc ore ork orn oro orr oru ou- ouc oue ouk oun ouo our rbb rbc rbe rbk rbn rbo rbr rbu rcb rcc rce rcn rco rcr rcu re- reb rec ree rek ren reo rer reu rkb rkc rke rkk rko rku rnb rnc rnn rno rnr rnu rob roc roe rok ron roo ror rou rrb rrc rrk rrn rrr rru rub ruc rue ruk run ruo rur ruu ubb ubc ube ubk ubn ubo ubr ubu ucb ucc uce uck ucn uco ucr ucu ueb uec uee uen uer ukb ukc uke ukk ukn ukr uku un- unb unc une unk unn uno unr unu uob uoc uoe uok uon uoo uor ur- urb urc ure urk urn uro urr uru uuc uue uun uur uuu