You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
4-[2-amino-8-(2-hydroxyphenyl)-7H-purin-6-yl]-N-(3-fluorophenyl)piperazine-1-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H21FN8O2
assistant