You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (4aR,7aS)-1-[(3,5-dimethylphenyl)methyl]-4-(1H-imidazol-2-ylmethyl)-2,3,4a,5,7,7a-hexahydrothieno[3,4-b]pyrazine 6,6-dioxide by IUPAC nomenclature, provide its molecular formula.
user
C19H26N4O2S
assistant