You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
7-[(2-phenyl-1H-indol-3-yl)methyl]-2-sulfanylidene-1,5,6,8-tetrahydropyrido[3,4-d]pyrimidin-4-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H20N4OS
assistant