a-a a-b aaa aab aam aao aar ab- aba abb abm abo abr ama amb amm amo amr aoa aob aom aoo aor ar- ara arb arm aro arr baa bab bam bao bar bba bbb bbm bbo bbr bma bmb bmm bmo bmr boa bob bom boo bor bra brb brm bro brr m-o m-r maa mab mam mao mar mba mbb mbm mbo mbr mma mmb mmm mmo mmr moa mob mom moo mor mra mrb mrm mro mrr oaa oab oam oao oar ob- oba obb obm obo obr om- oma omb omm omo omr oo- ooa oob oom ooo oor or- ora orb orm oro orr ra- raa rab ram rao rar rba rbb rbm rbo rbr rma rmb rmm rmo rmr roa rob rom roo ror rra rrb rrm rrr