N.N.N.O=P(O)(OC[C@H]1O[C@@H](n2cnc3cncnc32)[C@H](O)[C@@H]1O)OP(=O)(O)OP(=O)(O)OP(=O)(O)OC[C@H]1O[C@@H](n2cnc3cncnc32)[C@H](O)[C@@H]1O
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?