You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5Z)-5-[(5-methyl-1-phenylpyrrol-2-yl)methylidene]-2-phenylimino-1,3-thiazolidin-4-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H17N3OS
assistant