a-a a-b a-i aaa aab aai aao aar aax ab- aba abb abi abo abr abx ai- aia aib aii aio air aix aoa aob aoi aoo aor aox ar- ara arb ari aro arr arx ax- axa axi axo axr axx baa bab bai bao bar bax bba bbb bbi bbo bbr bbx bi- bia bib bii bio bir bix boa bob boi boo bor box bra brb bri bro brr brx bxb bxi bxo bxx ia- iaa iab iai iao iar iba ibb ibi ibo ibr ibx iia iib iii iio iir iix io- ioa iob ioi ioo ior ir- ira irb iri iro irr irx ixi o-i oaa oab oai oao oar oax ob- oba obb obi obo obr obx oia oib oii oio oir oo- ooa oob ooi ooo oor oox or- ora orb ori oro orr orx ox- oxa oxb oxi oxo oxx ra- raa rab rai rao rar rax rba rbb rbi rbo rbr rbx ria rib rii rio rir rix roa rob roi roo ror rox rra rrb rri rrr rxr xaa xar xbr xbx xia xii xio xix xoa xoi xoo xor xox xrx xxi xxo xxx