a-a a-b aaa aab aak aao aas aay ab- aba abb abk abo abs aby aka akb akk ako aks aoa aob aok aoo aos as- asa asb ask aso ass asy ay- aya ayk ayo ays baa bab bak bao bas bay bba bbb bbk bbo bbs bby bka bkb bkk bko bks boa bob bok boo bos boy bsa bsb bsk bso bss bsy by- bya byk byo bys ka- kaa kab kak kao kas kay kba kbb kbk kbo kbs kkb kkk kks kky koa kob kok koo kos koy ksa ksb ksk kso kss kya kyo kys oaa oab oak oao oas ob- oba obb obk obo obs oby oka okb okk oko oks oo- ooa oob ook ooo oos os- osa osb osk oso oss oya oyo oys saa sab sak sao sas say sba sbb sbk sbo sbs sby sk- ska skb skk sko sks sky soa sob sok soo sos soy ss- ssa ssb ssk sso sss sy- sya syb syk sys yaa yab yak yao yas yay ybs yby yka ykk yob yok yoo yos yoy ysa ysb ysk yso yss ysy yyb yys yyy