You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 5-[(1S)-1-phenylethyl]-2-(1H-pyrazol-5-yl)-6a,7,9,10-tetrahydro-[1,4]oxazino[3,4-h]pteridin-6-one .
user
C20H20N6O2
assistant