bbb bbi bbo bbr bbt bbx bi- bib bii bio bir bit bix bob boi boo bor bot box brb bri bro brr brt brx btb bti bto btr btt btx bxb bxi bxo bxx ibb ibi ibo ibr ibt ibx iib iii iio iir iit iix io- iob ioi ioo ior iot ir- irb iri iro irr irt irx itb iti ito itt itx ixi o-i ob- obb obi obo obr obt obx oib oii oio oir oit oo- oob ooi ooo oor oot oox or- orb ori oro orr ort orx ot- otb oti oto otr ott ox- oxb oxi oxo oxt oxx rbb rbi rbo rbr rbt rbx rib rii rio rir rit rix rob roi roo ror rot rox rrb rri rrr rrt rtb rti rto rtr rtt rtx rxr t-x tbb tbi tbo tbr tbt tib tii tio tir tit tix to- tob toi too tor tot tox trb tri tro trr trt trx ttb tti tto ttr ttt ttx txi txt xbr xbx xii xio xit xix xoi xoo xor xot xox xrt xrx xti xtr xtx xxi xxo xxx