Let M and N be foots of the perpendiculars drawn from the point \(\mathrm{P}(\mathrm{a}, \mathrm{a}, \mathrm{a})\) on the lines \(x-y=0, \mathrm{z}=1\) and \(x+y=0, \mathrm{z}=-1\) respectively and if \(\angle \mathrm{MPN}=90^{\circ}\) then \(\mathrm{a}^2=\)