You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(3-fluoro-4-methoxyphenyl)methyl]-N-methyl-3-[(2S)-2-methyl-3-oxo-1,4-benzoxazin-4-yl]propanamide is the IUPAC name of a molecule. Please give its molecular formula.
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C21H23FN2O4
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