You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[2-[(2,5-difluorophenyl)methyl]-4-methylpyrazol-3-yl]-2-(3,4-dimethoxyphenyl)acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H21F2N3O3
assistant