You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance (3Z,5E,7E,9E)-5-ethylidene-6-(4-hydroxyphenyl)-6,7-dimethylundeca-1,3,7,9-tetraene-2,10-diol .
user
C21H26O3
assistant