You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 21-oxa-22,23,24-triazapentacyclo[16.2.1.13,6.18,11.113,16]tetracosa-1(20),2,4,6(24),7,9,11,13(22),14,16,18-undecaene by IUPAC nomenclature, provide its molecular formula.
user
C20H13N3O
assistant