You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
8-[2-[methyl-(1-methylpiperidin-3-yl)amino]-2-oxoethyl]-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H28N2O3
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