You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2R)-1-amino-1-oxopropan-2-yl]-[(S)-(4-ethylphenyl)-thiophen-2-ylmethyl]azanium The above is the IUPAC name of a molecule. Write its molecular formula.
user
C16H21N2OS+
assistant