You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 3-[[2,4-difluoro-5-(6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[4,3-a]azepin-3-yl)phenyl]sulfamoyl]benzoate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20F2N4O4S
assistant