You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(7-butan-2-yl-2-methyl-6-oxo-7,8-dihydro-5H-pteridin-4-yl)amino]-4-ethyl-5-methylthiophene-3-carbonitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H24N6OS
assistant