You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 6-benzyl-4-methyl-2-propyl-4a,7,8,9a-tetrahydropurino[7,8-a]imidazole-1,3-dione is given. What is its corresponding molecular formula?
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C18H23N5O2
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