54. In the two vertical equations below, the same Chinese characters represent the same digits, and different Chinese characters represent different digits. The four-digit number represented by “学好数学” is $\qquad$.
$$
\begin{array}{r}
\text { 数 学 } \\
+ \text { 学 数 } \\
\hline 99
\end{array} \quad \begin{array}{r}
\text { 数 学 好 } \\
+ \text { 好 学 数 } \\
\hline \text { 学学好 学 }
\end{array}
$$
Answer: 1381