You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-oxo-2-(2-phenyl-5,6,8,9-tetrahydro-[1,2,4]triazolo[1,5-d][1,4]diazepin-7-yl)ethyl]azepan-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H25N5O2
assistant