Variable pairs of chords at right angles are drawn through any point $P$ (with eccentric angle $\frac{\pi}{4}$) on the ellipse $\frac{x^2}{4} + y^2 = 1$, to meet the ellipse at two points say $A$ and $B$. If the line joining $A$ and $B$ passes through a fixed point $Q(a,b)$ such that $a^2 + b^2$ has the value equal to $\frac{m}{n}$, where $m, n$ are respectively prime positive integers, then the value of $\frac{m+n}{3}$ is____.