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 5-chloro-3-(2,5-dichlorophenyl)-6-fluoro-2-[(1R)-1-(7H-purin-6-ylamino)ethyl]quinazolin-4-one is given. What is its corresponding molecular formula?
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C21H13Cl3FN7O
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