## MCIRGAME - Point Connection Game in a Circle

Đọc đề đẹp hơn ở:

https://codeforces.com/group/FLVn1Sc504/contest/274710/problem/O

https://codeforces.com/group/FLVn1Sc504/contest/274505/problem/O

https://codeforces.com/group/FLVn1Sc504/contest/274710/problem/O

https://codeforces.com/group/FLVn1Sc504/contest/274505/problem/O

English | Vietnamese |

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!

### Input

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 ≤ 150. Sample Input 2 -1

### Output

For each n, print in a single line the number of ways to connect the 2n numbers into pairs. Sample output 2

**Note : Big num!**Added by: | ~!(*(@*!@^& |

Date: | 2009-02-23 |

Time limit: | 1s |

Source limit: | 50000B |

Memory limit: | 1536MB |

Cluster: | Cube (Intel G860) |

Languages: | All except: ERL JS-RHINO NODEJS PERL6 VB.NET |

Resource: | Pre Shanghai 2004 |