You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[(2-chlorophenyl)methyl]-6-[4-(4-methoxyphenyl)piperazine-1-carbonyl]-5-methylthieno[2,3-d]pyrimidin-4-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C26H25ClN4O3S
assistant