You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4-oxo-6,7,8,9-tetrahydropyrimido[2,1-b][1,3]benzothiazol-2-yl)methyl 2-(4-methylphenoxy)acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20N2O4S
assistant