a-a a-b a-i aaa aab aai aao aas aax aay ab- aba abb abi abo abs abx aby ai- aia aib aii aio ais aix aiy aoa aob aoi aoo aos aox as- asa asb asi aso ass asx asy ax- axa axi axo axs axx ay- aya ayi ayo ays ayx baa bab bai bao bas bax bay bba bbb bbi bbo bbs bbx bby bi- bia bib bii bio bis bix biy boa bob boi boo bos box boy bsa bsb bsi bso bss bsx bsy bxb bxi bxo bxx by- bya byi byo bys ia- iaa iab iai iao ias iba ibb ibi ibo ibs ibx iby iia iib iii iio iis iix io- ioa iob ioi ioo ios is- isa isb isi iso iss isy ixi ixy iya iyo iys iyy o-i oaa oab oai oao oas oax ob- oba obb obi obo obs obx oby oia oib oii oio ois oo- ooa oob ooi ooo oos oox os- osa osb osi oso oss osx ox- oxa oxb oxi oxo oxx oxy oya oyi oyo oys saa sab sai sao sas sax say sba sbb sbi sbo sbs sbx sby sia sib sii sio sis six soa sob soi soo sos sox soy ss- ssa ssb ssi sso sss ssx sxi sxs sy- sya syb syi sys syx xaa xas xbx xia xii xio xis xix xoa xoi xoo xos xox xsa xsb xsi xss xxi xxo xxx xxy xyy yaa yab yai yao yas yax yay ybi ybs yby yii yio yis yob yoi yoo yos yox yoy ysa ysb ysi yso yss ysy yxa yxy yyb yys yyy