a-a a-b a-z aaa aab aad aar aaz ab- aba abb abd abr abz ad- ada adb add adr adz ar- ara arb ard arr arz az- aza azb azd azz baa bab bad bar baz bba bbb bbd bbr bda bdb bdd bdr bdz bra brb brd brr brz bza bzd bzr bzz daa dab dad dar daz dba dbb dbd dbr dbz dda ddb ddd ddr ddz dra drb drd drr drz dza dzb dzd dzr ra- raa rab rad rar raz rba rbb rbd rbr rda rdb rdd rdr rra rrb rrd rrr rza rzb zaa zab zad zar zaz zbb zbr zzr zzz