You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[1-(2-cyano-4-methylpyrrolidin-1-yl)-4-methyl-1-oxopentan-2-yl]-4-fluoro-1H-indole-2-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H25FN4O2
assistant