a-a a-b aaa aab aao aar aas aav ab- aba abb abo abr abs abv aoa aob aoo aor aos aov ar- ara arb aro arr ars arv as- asa asb aso asr ass asv av- ava avb avo avr avs baa bab bao bar bas bav bba bbb bbo bbr bbs boa bob boo bor bos bov bra brb bro brr brs brv bsa bsb bso bsr bss bsv bva bvb bvo bvr bvs bvv oaa oab oao oar oas oav ob- oba obb obo obr obs obv oo- ooa oob ooo oor oos oov or- ora orb oro orr ors orv os- osa osb oso osr oss osv ov- ova ovb ovo ovs ovv ra- raa rab rao rar ras rav rba rbb rbo rbr rbs roa rob roo ror ros rov rra rrb rrr rrs rsa rsb rso rsr rss rsv rva rvb rvo rvr rvs rvv saa sab sao sar sas sav sba sbb sbo sbr sbs sbv soa sob soo sor sos sov sr- sra srb sro srr srs srv ss- ssa ssb sso ssr sss ssv sva svb svo svr svs svv v-a vaa vab vao var vas vav vba vbo vbr vbs vbv voa vob voo vor vos vov vra vrb vrr vrs vsa vsb vso vsr vss vsv vva vvb vvo vvr vvs vvv