You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 18',18'-dimethylspiro[cyclopropane-1,8'-pentacyclo[10.8.1.12,6.016,21.011,22]docosa-1(20),2,4,6,9,11(22),12,14,16(21)-nonaene];ethane into its molecular formula.
user
C28H30
assistant