You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(3,4-dimethoxyphenyl)-2-[(3-methyl-2-oxo-3H-imidazo[1,2-c]quinazolin-5-yl)sulfanyl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20N4O4S
assistant