C[C@@H](Cc1ccc(C=O)cc1)NC[C@@H](O)c1ccc(O)c(NCO)c1.C[C@@H](Cc1ccc(C=O)cc1)NC[C@@H](O)c1ccc(O)c(NCO)c1.O=C(O)/C=C/C(=O)O
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?