You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by 1-[2-[(7R)-5-(1H-indol-4-ylmethyl)-6,7-dihydro-4H-pyrazolo[1,5-a]pyrazin-7-yl]ethyl]pyrrolidin-2-one ?
user
C21H25N5O
assistant