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 N-[2-(1,2,3,5,6,7-hexahydropyrrolizin-8-yl)ethyl]-2-oxo-3-propan-2-ylbenzimidazole-1-carboxamide ?
user
C20H28N4O2
assistant