You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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(2S)-2-(5-chloro-1,3-dimethylpyrazol-4-yl)-3-(2,4-dimethoxyphenyl)-1,2-dihydroquinazolin-4-one is the IUPAC name of a molecule. Please give its molecular formula.
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C21H21ClN4O3
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