You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 4-[[2-(dimethylamino)-4-methylpentyl]amino]-2,5-dimethylthieno[2,3-d]pyrimidine-6-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H28N4O2S
assistant