You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(5,7-dimethyl-2-oxo-1H-pyrazolo[1,5-a]pyrimidin-6-yl)-N-[3-(dimethylsulfamoyl)phenyl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21N5O4S
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