You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(3S)-3-benzyl-1-methyl-2-oxoindol-3-yl]-N-(2-oxo-1H-pyridin-3-yl)acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C23H21N3O3
assistant