COC(=O)C1(C(=O)OC)CC(=O)c2c(OC(=O)c3cccc(OC)c3C#N)ccc(OC(=O)c3cccc(OC)c3C#N)c2C1
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?