1. Given
$$
\begin{aligned}
A= & \left\{x \mid x^{2}-4 x+3<0, x \in \mathbf{R}\right\}, \\
B= & \left\{x \mid 2^{1-x}+a \leqslant 0, x^{2}-2(a+7) x+5 \leqslant\right. \\
& 0, x \in \mathbf{R}\} .
\end{aligned}
$$

If $A \subseteq B$, then the range of real number $a$ is