You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(5R,7S)-2-(3-chlorophenyl)-1-oxo-2-azaspiro[4.5]decan-7-yl]pyridine-2-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H22ClN3O2
assistant