12、Given the function $f(x)=\frac{a}{x}-x$, for any $x \in(0,1)$, it holds that $f(x) \cdot f(1-x) \geq 1$. Then the range of the real number $a$ is $\qquad$
12、 $\left\{a \mid a \geq 1\right.$ or $\left.a \leq-\frac{1}{4}\right\}$