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 1-[3-(7-methyl-5,6,8,9-tetrahydro-[1,2,4]triazolo[4,3-d][1,4]diazepin-3-yl)piperidin-1-yl]-2-phenoxyethanone .
user
C20H27N5O2
assistant