You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 5-chloro-N-[2-(3-cyano-5,5-dimethyl-4-oxocyclohex-2-en-1-yl)ethyl]-N-methyl-1-benzofuran-2-carboxamide into molecular formula.
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C21H21ClN2O3
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