You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(3R)-1-[[(3S)-2,3-dihydro-1,4-benzodioxin-3-yl]methyl]-5-methyl-2-oxo-3H-indol-3-yl]acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H20N2O4
assistant