You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-[(2R)-2-(2-chlorophenyl)-2-methoxyethyl]-5,6,7,8-tetrahydro-4H-cyclohepta[d][1,2]oxazole-3-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21ClN2O3
assistant