a-a a-b a-i aaa aab aai aas aay ab- aba abb abi abs aby ai- aia aib aii ais aiy as- asa asb asi ass asy ay- aya ayi ays baa bab bai bas bay bba bbb bbi bbs bby bi- bia bib bii bis biy bsa bsb bsi bss bsy by- bya byi bys ia- iaa iab iai ias iba ibb ibi ibs iby iia iib iii iis is- isa isb isi iss isy iya iys iyy saa sab sai sas say sba sbb sbi sbs sby sia sib sii sis ss- ssa ssb ssi sss sy- sya syb syi sys yaa yab yai yas yay ybi ybs yby yii yis ysa ysb ysi yss ysy yyb yys yyy