You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[2-[6-(2-methoxyphenoxy)pyrazin-2-yl]pyrrolidin-1-yl]-(2-methylpyrazol-3-yl)methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H21N5O3
assistant