You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[5-[(5-bromo-1-methyl-2-oxoindol-3-ylidene)methyl]-4-hydroxy-2-sulfanylidene-1,3-thiazol-3-yl]ethanesulfonic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C15H13BrN2O5S3
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