You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[4-(2-hydroxyphenyl)piperazin-1-yl]-2-(5,6,7,8-tetrahydroquinolin-4-yloxy)ethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H25N3O3
assistant