You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2S)-1-amino-1-oxopropan-2-yl] 2-[3-(4-nitrophenyl)-1-phenylpyrazol-4-yl]acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H18N4O5
assistant