Let α_1, α_2, …, α_7 be the roots of the equation x^7+3 x^5-13 x^3-15 x=0 and |α_1| ≥|α_2| ≥ … ≥|α_7|. Then α_1 α_2-α_3 α_4+α_5 α_6 is equal to ____

Let $\displaystyle \alpha_1, \alpha_2, \ldots, \alpha_7$ be the roots of the equation $\displaystyle x^7+3 x^5-13 x^3-15 x=0$ and $\displaystyle \left|\alpha_1\right| \geq\left|\alpha_2\right| \geq \ldots \geq\left|\alpha_7\right|$. Then $\displaystyle \alpha_1 \alpha_2-\alpha_3 \alpha_4+\alpha_5 \alpha_6$ is equal to $\displaystyle \_\_\_\_$