-er bbb bbe bbi bbo bbr bbx be- beb bee bei beo ber bex bi- bib bie bii bio bir bix bob boe boi boo bor box brb bre bri bro brr brx bxb bxi bxo bxx ebb ebe ebi ebo ebr ebx eeb eee eeo eer eex eib eie eii eio eir eix eo- eob eoe eoi eoo eor erb ere eri ero err ex- exe exi exo exr exx ibb ibe ibi ibo ibr ibx ie- iee iei ier iex iib iie iii iio iir iix io- iob ioe ioi ioo ior ir- irb ire iri iro irr irx ixe ixi o-i ob- obb obe obi obo obr obx oeb oee oei oeo oer oex oib oie oii oio oir oo- oob ooi ooo oor oox or- orb ore ori oro orr orx ox- oxb oxi oxo oxx rbb rbe rbi rbo rbr rbx re- reb ree rei reo rer rex rib rie rii rio rir rix rob roe roi roo ror rox rrb rri rrr rxr xbe xbr xbx xee xer xex xie xii xio xix xoi xoo xor xox xrx xxi xxo xxx