You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[3-[5-[(3-fluorophenyl)methyl]-1,3-oxazol-2-yl]-3-methylpiperidin-1-yl]-pyrazin-2-ylmethanone is the IUPAC name of a molecule. Please give its molecular formula.
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C21H21FN4O2
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