You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(4-tert-butylpyridin-1-ium-1-yl)-3-(5-chlorothiophen-2-yl)-N-ethyl-3-oxopropanimidothioate is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H21ClN2OS2
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