O=C1C=CC(=O)c2c1ccc1c3ccccc3n(CCCCCCCCn3c4ccccc4c4ccc5c(c43)C(=O)C=CC5=O)c21
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?