a-a a-b a-i aaa aab aai aak aao aar ab- aba abb abi abk abo abr ai- aia aib aii aik aio air aka akb aki akk ako akr aoa aob aoi aok aoo aor ar- ara arb ari ark aro arr baa bab bai bak bao bar bba bbb bbi bbk bbo bbr bi- bia bib bii bik bio bir bka bkb bkk bko bkr boa bob boi bok boo bor bra brb bri brk bro brr ia- iaa iab iai iao iar iba ibb ibi ibk ibo ibr iia iib iii iio iir ika ikb iki ikk iko ikr io- ioa iob ioi ioo ior ir- ira irb iri irk iro irr ka- kaa kab kai kak kao kar kba kbb kbi kbk kbo kbr kia kib kii kik kio kir kkb kki kkk kkr koa kob koi kok koo kor kra kri krk kro krr o-i oaa oab oai oak oao oar ob- oba obb obi obk obo obr oia oib oii oik oio oir oka okb oki okk oko okr oo- ooa oob ooi ook ooo oor or- ora orb ori ork oro orr ra- raa rab rai rak rao rar rba rbb rbi rbk rbo rbr ria rib rii rik rio rir rkb rkk rko roa rob roi rok roo ror rra rrb rri rrk rrr