You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(1R,3R)-3-hydroxy-7-oxaspiro[3.5]nonan-1-yl]-2-(5,6,7,8-tetrahydronaphthalen-2-yl)acetamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H27NO3
assistant