You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl 3-methyl-1-pyridin-2-yl-6-thiophen-2-ylpyrazolo[3,4-b]pyridine-4-carboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H14N4O2S
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