O=C1C(c2ccccc2)=C(c2ccccc2)C(c2ccc(Sc3ccc(C4=C(c5ccccc5)C(=O)C(c5ccccc5)=C4c4ccccc4)cc3)cc2)=C1c1ccccc1
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?