You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-methyl-N-[[4-(methylsulfonylmethyl)phenyl]methyl]-2-oxo-3H-benzimidazole-5-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H19N3O4S
assistant