-er bbb bbe bbn bbo bbr bbx be- beb bee ben beo ber bex bnb bne bnn bno bnr bnx bob boe bon boo bor box brb bre brn bro brr brx bxb bxn bxo bxx ebb ebe ebn ebo ebr ebx eeb eee een eeo eer eex en- enb ene enn eno enr eo- eob eoe eon eoo eor erb ere ern ero err ex- exe exo exr exx nbb nbe nbn nbo nbr nbx ne- neb nee nen neo ner nex nnb nne nnn nno no- nob noe non noo nor nox nrb nre nrn nro nrr nrx ob- obb obe obn obo obr obx oeb oee oen oeo oer oex on- onb one onn ono onr onx oo- oob oon ooo oor oox or- orb ore orn oro orr orx ox- oxb oxn oxo oxx rbb rbe rbn rbo rbr rbx re- reb ree ren reo rer rex rnb rnn rno rnr rob roe ron roo ror rox rrb rrn rrr rxr xbe xbr xbx xee xen xer xex xno xon xoo xor xox xrx xxo xxx