You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-ethyl-6-[(2E)-4-(5-ethylpyridin-3-yl)penta-2,4-dien-2-yl]-6-methyl-5-methylidenepiperazine-2-thione is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H27N3S
assistant