You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[(2S)-butan-2-yl]-N-[1-[(2-methylphenyl)methyl]pyrazol-4-yl]benzenesulfonamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H25N3O2S
assistant