You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(6aR,10aR)-10a-methyl-5,6,6a,8,9,10-hexahydropyrido[2,3-h]quinazolin-7-yl]-[4-(5-methyltetrazol-1-yl)phenyl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23N7O
assistant