CC(=O)OC1COC(N2C(=O)/C(=N\Nc3ccc([N+](=O)[O-])cc3)c3cc(Br)c([N+](=O)[O-])cc32)C(OC(C)=O)C1OC(C)=O
A lower number of pka indicates that the acid dissociates more entirely in water. What is pka of the molecule?