You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(2S)-pentan-2-yl]-2-[4-[3-(trifluoromethyl)phenyl]piperazin-1-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H26F3N3O
assistant