You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 3-[4-(difluoromethoxy)-3-ethoxyphenyl]-3-(4-nitro-3-oxo-1H-isoindol-2-yl)propanoic acid into molecular formula.
user
C20H18F2N2O7
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