## 1066:Game of Connections

- 总时间限制:
- 1000ms
- 内存限制:
- 65536kB

- 描述
- This is a small but ancient game. You are supposed to write down the numbers 1, 2, 3, . . . , 2n - 1, 2n consecutively in clockwise order on the ground to form a circle, and then, to draw some straight line segments to connect them into number pairs. Every number must be connected to exactly one another.

And, no two segments are allowed to intersect.

It's still a simple game, isn't it? But after you've written down the 2n numbers, can you tell me in how many different ways can you connect the numbers into pairs? Life is harder, right?
- 输入
- Each line of the input file will be a single positive number n, except the last line, which is a number -1.

You may assume that 1 <= n <= 100.
- 输出
- For each n, print in a single line the number of ways to connect the 2n numbers into pairs.
- 样例输入
2
3
-1

- 样例输出
2
5

- 来源
- Shanghai 2004 Preliminary

- 全局题号
- 1086
- 添加于
- 2012-09-05
- 提交次数
- 18
- 尝试人数
- 3
- 通过人数
- 0