You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[4-[[4-chloro-3-(trifluoromethyl)phenyl]carbamoylamino]-3-fluorophenoxy]-N-methylpyridine-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H15ClF4N4O3
assistant