You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(3R)-3-methylpiperazin-1-yl]-[2-(5H-pyrimido[5,4-d][2]benzazepin-2-ylamino)-1,3-thiazol-4-yl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H21N7OS
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