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 N-[3,3-dimethyl-5-(2-methylpropyl)-4-oxo-2H-1,5-benzoxazepin-8-yl]-2-thiophen-2-ylacetamide ?
user
C21H26N2O3S
assistant