A charge $$+q$$ is placed at each of the points $$x = x_0$$, $$x = 3x_0$$, $$x = 5x_0$$, $$x = 7x_0 \ldots \infty$$ on the x-axis and a charge $$-q$$ is placed at each of the points $$x = 2x_0$$, $$x = 4x_0$$, $$x = 6x_0$$, $$x = 8x_0 \ldots \infty$$ where $$x_0$$ is a positive constant. Take the electric potential at a point due to a charge $$q$$ at a distance $$r$$ from it to be $$\frac{1}{4\pi\epsilon_0}\frac{q}{r}$$. The electric potential at the origin due to the above system of charges is