The structure of a peptide is given below

If the absolute values of the net charge of the peptide at $\mathrm{pH}=2, \mathrm{pH}=6$, and $\mathrm{pH}=11$ are $\left|\mathrm{z}_1\right|,\left|\mathrm{z}_2\right|$ and $\left|z_3\right|$, respectively, then what is $\left|z_1\right|+\left|z_2\right|+\left|z_3\right|$ ?