Functions $F(a, b)$ and $G(a, b)$ are defined as follows: $F(a, b) = (a − b)^2$ and $G(a, b) = \mid a − b\mid$, where $\mid x \mid$ represents the absolute value of $x$. What would be the value of $G(F(1, 3), G(1, 3))$?