You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 16-methyl-6-(2-pyridin-2-ylethynyl)-1,4,9,12-tetrazatetracyclo[8.7.0.03,8.012,16]heptadeca-3(8),4,6,9-tetraen-2-one into molecular formula.
user
C21H19N5O
assistant