You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[[5-(4-methyl-2-oxo-4-sulfanylpentyl)imino-6,7,8,9-tetrahydrobenzo[7]annulen-2-yl]oxy]butanoic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H29NO4S
assistant