Let $m, n$ be positive integers and the quadratic equation $\displaystyle 4x^2 + mx + n = 0$ has two distinct real roots $p$ and $q$ $(p \leq q)$. Also, the quadratic equations $\displaystyle x^2 - px + 2q = 0$ and $\displaystyle x^2 - qx + 2p = 0$ have a common root say $\displaystyle \alpha$. If $p$ and $q$ are rational, then uncommon root of the equation $\displaystyle x^2 - px + 2q = 0$ and $\displaystyle x^2 - qx + 2p = 0$ is equal to