Nc1ncnc2c1ncn2C1OC(COC2C(CO)OC(OC(C(=O)O)C(O)C(OP(=O)(O)O)C(O)C(=O)O)C(O)C2O)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?