You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-[(1R,3S,5R)-3-(2-fluoroethylcarbamoyl)-2-azabicyclo[3.1.0]hexan-2-yl]-2-oxoethyl]indazole-3-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H20FN5O3
assistant