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 2-(4-chloroanilino)-4-(3-chloro-4-methylanilino)-7,8-dihydro-6H-quinazolin-5-one is given. What is its corresponding molecular formula?
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C21H18Cl2N4O
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