a-a a-b aaa aab aad aak aao aar ab- aba abb abd abk abo abr ad- ada adb add adk ado adr aka akb akd akk ako akr aoa aob aod aok aoo aor ar- ara arb ard ark aro arr baa bab bad bak bao bar bba bbb bbd bbk bbo bbr bda bdb bdd bdk bdo bdr bka bkb bkk bko bkr boa bob bod bok boo bor bra brb brd brk bro brr daa dab dad dak dao dar dba dbb dbd dbk dbo dbr dda ddb ddd ddk ddo ddr dka dkb dkk dko dkr doa dob dod dok doo dor dra drb drd drk dro drr ka- kaa kab kad kak kao kar kba kbb kbd kbk kbo kbr kda kdb kdk kdo kdr kkb kkk kkr koa kob kod kok koo kor kra krd krk kro krr oaa oab oad oak oao oar ob- oba obb obd obk obo obr oda odb odd odo odr oka okb okd okk oko okr oo- ooa oob ood ook ooo oor or- ora orb ord ork oro orr ra- raa rab rad rak rao rar rba rbb rbd rbk rbo rbr rda rdb rdd rdo rdr rkb rkk rko roa rob rod rok roo ror rra rrb rrd rrk rrr