You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (4Z)-2-[(Z)-but-1-en-3-ynyl]-1,3,3,6-tetramethyl-7,8-didehydro-6,9-dihydrocyclopenta[8]annulene;methane into its molecular formula.
user
C21H28
assistant