You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(3aR,6aS)-5-(2,4-difluorophenyl)-4,6-dioxo-3a,6a-dihydropyrrolo[3,4-d]triazol-3-yl]-N-(2,4-dichlorophenyl)acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H11Cl2F2N5O3
assistant