You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
cyclobutyl-[3-[5-(3-fluoroanilino)imidazo[5,1-b][1,3]thiazol-7-yl]piperidin-1-yl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H23FN4OS
assistant