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 1-[(2S)-but-3-yn-2-yl]-3-[(2S,3R)-2-(3,4-difluorophenyl)oxolan-3-yl]-1-methylurea ?
user
C16H18F2N2O2
assistant