a-a a-b aaa aab aao aas aav aay ab- aba abb abo abs abv aby aoa aob aoo aos aov as- asa asb aso ass asv asy av- ava avb avo avs avy ay- aya ayo ays baa bab bao bas bav bay bba bbb bbo bbs bby boa bob boo bos bov boy bsa bsb bso bss bsv bsy bva bvb bvo bvs bvv by- bya byo bys oaa oab oao oas oav ob- oba obb obo obs obv oby oo- ooa oob ooo oos oov os- osa osb oso oss osv ov- ova ovb ovo ovs ovv oya oyo oys saa sab sao sas sav say sba sbb sbo sbs sbv sby soa sob soo sos sov soy ss- ssa ssb sso sss ssv sva svb svo svs svv svy sy- sya syb sys v-a vaa vab vao vas vav vay vba vbo vbs vbv voa vob voo vos vov voy vsa vsb vso vss vsv vva vvb vvo vvs vvv yaa yab yao yas yav yay ybs yby yob yoo yos yoy ysa ysb yso yss ysy yva yvo yvy yyb yys yyy