O=C(N[C@@H](Cc1ccccc1)C(=O)OCc1ccccc1)c1nc[nH]c1C(=O)N[C@@H](Cc1ccccc1)C(=O)OCc1ccccc1
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?