-er a-a a-b a-t aaa aab aae aar aat aav ab- aba abb abe abr abt abv aea aeb aee aer aet aev ar- ara arb are arr art arv at- ata atb ate atr att atv av- ava avb ave avr avt baa bab bae bar bat bav bba bbb bbe bbr bbt be- bea beb bee ber bet bev bra brb bre brr brt brv bta btb bte btr btt btv bva bvb bve bvr bvt bvv eaa eab eae ear eat eav eba ebb ebe ebr ebt ebv eea eeb eee eer eet eev era erb ere err ert erv eta etb ete etr ett etv eva evb eve evr evt evv ra- raa rab rae rar rat rav rba rbb rbe rbr rbt re- rea reb ree rer ret rev rra rrb rrr rrt rta rtb rte rtr rtt rtv rva rvb rve rvr rvt rvv taa tab tae tar tat tav tba tbb tbe tbr tbt tbv te- tea teb tee ter tet tev tra trb tre trr trt trv tta ttb tte ttr ttt ttv tva tvb tve tvr tvt v-a v-e vaa vab vae var vat vav vba vbr vbv vea veb vee ver vet vra vrb vre vrr vrt vta vtb vte vtr vtt vtv vva vvb vvr vvt vvv