a-a a-b aaa aab aad aao aar aax ab- aba abb abd abo abr abx ad- ada adb add ado adr adx aoa aob aod aoo aor aox ar- ara arb ard aro arr arx ax- axa axo axr axx baa bab bad bao bar bax bba bbb bbd bbo bbr bbx bda bdb bdd bdo bdr bdx boa bob bod boo bor box bra brb brd bro brr brx bxb bxd bxo bxx daa dab dad dao dar dax dba dbb dbd dbo dbr dbx dda ddb ddd ddo ddr ddx doa dob dod doo dor dox dra drb drd dro drr drx dxd dxo dxr dxx oaa oab oad oao oar oax ob- oba obb obd obo obr obx oda odb odd odo odr oo- ooa oob ood ooo oor oox or- ora orb ord oro orr orx ox- oxa oxb oxo oxx ra- raa rab rad rao rar rax rba rbb rbd rbo rbr rbx rda rdb rdd rdo rdr rdx roa rob rod roo ror rox rra rrb rrd rrr rxr xaa xad xar xbr xbx xda xdb xdr xoa xod xoo xor xox xrd xrx xxo xxx