-er bbb bbe bbi bbr bbt bbx be- beb bee bei ber bet bex bi- bib bie bii bir bit bix brb bre bri brr brt brx btb bte bti btr btt btx bxb bxi bxx ebb ebe ebi ebr ebt ebx eeb eee eer eet eex eib eie eii eir eit eix erb ere eri err ert etb ete eti etr ett etx ex- exe exi exr ext exx ibb ibe ibi ibr ibt ibx ie- iee iei ier iet iex iib iie iii iir iit iix ir- irb ire iri irr irt irx itb ite iti itt itx ixe ixi rbb rbe rbi rbr rbt rbx re- reb ree rei rer ret rex rib rie rii rir rit rix rrb rri rrr rrt rtb rte rti rtr rtt rtx rxr t-x tbb tbe tbi tbr tbt te- teb tee tei ter tet tex tib tie tii tir tit tix trb tre tri trr trt trx ttb tte tti ttr ttt ttx txe txi txt xbe xbr xbx xee xer xet xex xie xii xit xix xrt xrx xti xtr xtx xxi xxx