a-a a-b aaa aab aad aak aar ab- aba abb abd abk abr ad- ada adb add adk adr aka akb akd akk akr ar- ara arb ard ark arr baa bab bad bak bar bba bbb bbd bbk bbr bda bdb bdd bdk bdr bka bkb bkk bkr bra brb brd brk brr daa dab dad dak dar dba dbb dbd dbk dbr dda ddb ddd ddk ddr dka dkb dkk dkr dra drb drd drk drr ka- kaa kab kad kak kar kba kbb kbd kbk kbr kda kdb kdk kdr kkb kkk kkr kra krd krk krr ra- raa rab rad rak rar rba rbb rbd rbk rbr rda rdb rdd rdr rkb rkk rra rrb rrd rrk rrr