You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4-benzylpiperazin-1-yl)-(5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H23N5O
assistant