OC[C@@H]1O[C@H](OC2[C@@H](O)[C@@H](O)[C@@H](O)O[C@@H]2CO)[C@H](O)[C@@H](O)[C@@H]1OC1O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]1O
A higher pKa value denotes a less powerful acid. What is this molecule's pka value?