You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 3-ethyl-2-methyl-5-nitro-N-(1,2,3,4-tetrahydroisoquinolin-1-ylmethyl)imidazol-4-amine into molecular formula.
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C16H21N5O2
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