You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[[2-(dimethylamino)pyridin-3-yl]methyl]-3-[(1R,2S)-2-(3-fluorophenyl)cyclopropyl]urea is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21FN4O
assistant