You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2R)-2-[(2R)-1-ethylpyrrolidin-2-yl]pyrrolidin-1-yl]-[4-(tetrazol-1-yl)phenyl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H24N6O
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