You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(2-chlorophenyl)methyl]-2-[[(1R)-1,7-dimethyl-3-oxo-1,2-dihydroinden-4-yl]oxy]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20ClNO3
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