-er a-a a-b aaa aab aad aae aar ab- aba abb abd abe abr ad- ada adb add ade adr aea aeb aed aee aer ar- ara arb ard are arr baa bab bad bae bar bba bbb bbd bbe bbr bda bdb bdd bde bdr be- bea beb bed bee ber bra brb brd bre brr daa dab dad dae dar dba dbb dbd dbe dbr dda ddb ddd dde ddr de- dea deb ded dee der dra drb drd dre drr eaa eab ead eae ear eba ebb ebd ebe ebr ed- eda edb edd ede edr eea eeb eed eee eer era erb erd ere err ra- raa rab rad rae rar rba rbb rbd rbe rbr rda rdb rdd rde rdr re- rea reb red ree rer rra rrb rrd rrr