You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2R)-1-oxo-1-(3-oxo-2,4-dihydroquinoxalin-1-yl)propan-2-yl] 2-methoxy-5-methylbenzoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N2O5
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