a-a a-b aaa aab aah aao aar ab- aba abb abh abo abr aha ahb ahh aho ahr aoa aob aoh aoo aor ar- ara arb arh aro arr baa bab bah bao bar bba bbb bbh bbo bbr bha bhb bhh bho bhr boa bob boh boo bor bra brb brh bro brr haa hab hah hao har hba hbb hbh hbo hbr hha hhb hhh hho hhr hoa hob hoh hoo hor hr- hra hrb hrh hro hrr oaa oab oah oao oar ob- oba obb obh obo obr oha ohh oho ohr oo- ooa oob ooh ooo oor or- ora orb orh oro orr ra- raa rab rah rao rar rba rbb rbh rbo rbr rh- rha rhb rhh rho rhr roa rob roh roo ror rra rrb rrh rrr