a-a a-b aaa aab aan aao aas aav ab- aba abb abn abo abs abv an- ana anb ann ano ans anv aoa aob aon aoo aos aov as- asa asb asn aso ass asv av- ava avb avn avo avs baa bab ban bao bas bav bba bbb bbn bbo bbs bna bnb bnn bno bns bnv boa bob bon boo bos bov bsa bsb bsn bso bss bsv bva bvb bvn bvo bvs bvv naa nab nan nao nas nav nba nbb nbn nbo nbs nbv nna nnb nnn nno nns nnv no- noa nob non noo nos nov nsa nsb nsn nso nss nsv nva nvb nvn nvv oaa oab oan oao oas oav ob- oba obb obn obo obs obv on- ona onb onn ono ons oo- ooa oob oon ooo oos oov os- osa osb osn oso oss osv ov- ova ovb ovo ovs ovv saa sab san sao sas sav sba sbb sbn sbo sbs sbv sna snb snn sno sns snv soa sob son soo sos sov ss- ssa ssb ssn sso sss ssv sva svb svn svo svs svv v-a vaa vab van vao vas vav vba vbo vbs vbv vn- vna vno vns vnv voa vob von voo vos vov vsa vsb vsn vso vss vsv vva vvb vvo vvs vvv