-er bbb bbe bbk bbn bbo bbr be- beb bee bek ben beo ber bkb bke bkk bkn bko bkr bnb bne bnk bnn bno bnr bob boe bok bon boo bor brb bre brk brn bro brr ebb ebe ebk ebn ebo ebr eeb eee eek een eeo eer ekb eke eko ekr en- enb ene enk enn eno enr eo- eob eoe eok eon eoo eor erb ere erk ern ero err kbb kbe kbk kbn kbo kbr ke- keb kee kek ken keo ker kkb kke kkk kkn kkr kn- kne knk knn kno knr kob koe kok kon koo kor krk krn kro krr nbb nbe nbk nbn nbo nbr ne- neb nee nek nen neo ner nke nkk nkn nko nkr nnb nne nnk nnn nno no- nob noe nok non noo nor nrb nre nrk nrn nro nrr ob- obb obe obk obn obo obr oeb oee oen oeo oer okb oke okk oko okr on- onb one onk onn ono onr oo- oob ook oon ooo oor or- orb ore ork orn oro orr rbb rbe rbk rbn rbo rbr re- reb ree rek ren reo rer rkb rke rkk rko rnb rnn rno rnr rob roe rok ron roo ror rrb rrk rrn rrr