You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(3,4-difluorophenoxy)-N-hydroxy-6-methyl-N'-(2-methylbutan-2-yl)pyridine-3-carboximidamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21F2N3O2
assistant