Circle

Let the circle \(C_1: x^2+y^2-2(x+y)+1=0\) and \(\mathrm{C_2}\) be a circle having centre at \((-1,0)\) and radius 2 . If the line of the common chord of \(\mathrm{C}_1\) and \(\mathrm{C}_2\) intersects the \(\mathrm{y}\)-axis at the point \(\mathrm{P}\), then the square of the distance of P from the centre of \(\mathrm{C_1}\) is: