You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named N-[(2-chlorophenyl)methyl]-2-[1-(1-ethylpyrazole-3-carbonyl)piperidin-3-yl]-N-methylacetamide by IUPAC nomenclature, provide its molecular formula.
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C21H27ClN4O2
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