You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 3-ethyl-5-methyl-4-methylidene-1-(3-methylpentyl)-6-[(2-oxoimidazolidin-1-yl)methyl]thieno[2,3-d]pyrimidin-2-one into molecular formula.
user
C20H30N4O2S
assistant