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-[[3-[4-(4-fluorophenyl)piperazin-1-yl]azetidin-1-yl]methyl]-3-hydroxypiperidin-1-yl]ethanone .
user
C21H31FN4O2
assistant