NCC1O[C@@H](OC2C(N)C[C@H](N)[C@@H](O[C@H]3OC(CO)C(O)C(N)C3O)C2O)C(N)C(O)C1O
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?