You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[2-(2,4-dimethoxyanilino)-2-oxoethyl]-2-(2-methoxyethyl)-4-oxothieno[2,3-d]pyrimidine-5-carboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H21N3O7S
assistant