O=C(C[n+]1ccccc1)N/N=C(\Cc1nc2ccc([N+](=O)[O-])cc2nc1O)C(=O)Nc1cc(Cl)c(Cl)cc1Cl.[Cl-]
Hydrogen bond acceptor is the chemical compound which contains the lone electron pairs that participate in the hydrogen bond formation. How many hydrogen bond acceptors does the molecule contain?