a-a a-b aaa aab aaf aan aar aav ab- aba abb abf abn abr abv af- afa afb aff afn afr afv an- ana anb anf ann anr anv ar- ara arb arf arn arr arv av- ava avb avf avn avr baa bab baf ban bar bav bba bbb bbf bbn bbr bfa bfb bff bfn bfr bfv bna bnb bnf bnn bnr bnv bra brb brf brn brr brv bva bvb bvn bvr bvv faa fab faf fan far fav fba fbb fbf fbn fbr ffa fff ffn ffr ffv fna fnb fnf fnn fnr fnv fra frb frf frn frr fva naa nab naf nan nar nav nba nbb nbf nbn nbr nbv nfa nfb nff nfn nfr nfv nna nnb nnf nnn nnv nra nrb nrf nrn nrr nrv nva nvb nvn nvv ra- raa rab raf ran rar rav rba rbb rbf rbn rbr rfa rfb rff rfn rfr rfv rna rnb rnn rnr rnv rra rrb rrf rrn rrr rva rvb rvf rvn rvr rvv v-a vaa vab van var vav vba vbr vbv vfa vfb vff vfn vfr vfv vn- vna vnf vnr vnv vra vrb vrf vrn vrr vva vvb vvr vvv