You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (5Z)-5-[(9-methyl-4-oxo-2-pyrrolidin-1-ylpyrido[1,2-a]pyrimidin-3-yl)methylidene]-3-prop-2-enyl-2-sulfanylidene-1,3-thiazolidin-4-one .
user
C20H20N4O2S2
assistant