You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-benzyl-3-(2-chloroethyl)-N-[(4-methoxyphenyl)methyl]-4-oxoimidazo[5,1-d][1,2,3,5]tetrazine-8-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H21ClN6O3
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