You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[4-(2-amino-2-oxoethyl)sulfonylbenzoyl]-2,3,3a,4,5,6,7,7a-octahydroindole-2-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H22N2O6S
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