You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-ethyl-2-[(3-fluorophenyl)methyl]-3-[[2-(propan-2-ylsulfamoylmethyl)phenyl]methyl]guanidine is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H29FN4O2S
assistant