You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(3,7-dimethyl-1H-indol-2-yl)methyl]-3-(3-methoxypropyl)piperidine-3-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H30N2O3
assistant