-er a-a a-b aaa aab aae aar aav ab- aba abb abe abr abv aea aeb aee aer aev ar- ara arb are arr arv av- ava avb ave avr baa bab bae bar bav bba bbb bbe bbr be- bea beb bee ber bev bra brb bre brr brv bva bvb bve bvr bvv eaa eab eae ear eav eba ebb ebe ebr ebv eea eeb eee eer eev era erb ere err erv eva evb eve evr evv ra- raa rab rae rar rav rba rbb rbe rbr re- rea reb ree rer rev rra rrb rrr rva rvb rve rvr rvv v-a v-e vaa vab vae var vav vba vbr vbv vea veb vee ver vra vrb vre vrr vva vvb vvr vvv