C=C1C(=O)[C@]23C[C@H]1CC[C@H]2[C@]1(C)[C@@H](OC(C)=O)CC[C@@](C)(C(=O)O)[C@H]1C[C@@H]3O
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?