You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(4-cyanophenyl)methyl]-N-[[4-[(2-hydroxy-3,4-dioxocyclobuten-1-yl)amino]phenyl]methyl]-2-methoxybenzenesulfonamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C26H21N3O6S
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