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 1-[2-(3,4-dihydro-2H-1,5-benzodioxepin-7-yl)pyrrolidin-1-yl]-2-imidazo[2,1-b][1,3]thiazol-6-ylethanone ?
user
C20H21N3O3S
assistant