P2561 [AHOI2002] Black and White Tiles

Description

![](https://cdn.luogu.com.cn/upload/pic/1685.png) ![](https://cdn.luogu.com.cn/upload/pic/1686.png)

Input Format

One line containing a positive integer $n$, where $n \leq 20$.

Output Format

Output, in one line, the solution $s$ (the number of digits of the answer does not exceed 200).

Explanation/Hint

Translated by ChatGPT 5