Sea $p$ un primo tal que $p \equiv 1 (\text {mod}4)$ . Evalúe \ [\sum_{k=1}^{p-1} \left( \left \lfloor \frac{2k^2}{p}\right \rfloor - 2 \left \lfloor {\frac{k^2}{p}}\right \rfloor \right)\]