【Solution】Solution: The largest three-digit even number is 998,
To satisfy $A$ being the smallest and $A<B<C<D<E$, then $E$ is at most 998, $D$ is at most 996, $C$ is at most 994, and $B$ is at most 992,
$$
\begin{array}{l}
4306-(998+996+994+992) \\
=4306-3980 \\
=326,
\end{array}
$$

Therefore, $A$ is at least 326. The answer is: 326.
5. (3 points) Three-digit even numbers $A, B, C, D, E$ satisfy $A<B<C<D<E$. If $A+B+C+D+E=4306$, then $A$ is the smallest. $\qquad$