You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-methyl-1-[(5-phenyl-1,3-oxazol-4-yl)methyl]-3-spiro[2-oxabicyclo[3.2.0]heptane-7,1'-cyclobutane]-6-ylguanidine;hydroiodide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H27IN4O2
assistant