You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(5-bromothiophen-2-yl)methyl]-3-ethyl-2-[2-hydroxy-2-(4-methoxyphenyl)ethyl]-1-methylguanidine is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H24BrN3O2S
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