Circle And Chords

easy
1. You are given a number N.
2. There are 2*N points on a circle. You have to draw N non-intersecting chords on a circle.
3. You have to find the number of ways in which these chords can be drawn.

Input Format

A number N

Output Format

Check the sample output and question video.

Constraints

1 <= N <= 1000
1 <= arr[i] <= 100

Notice

Try First, Check Solution later

1. You should first read the question and watch the question video.
2. Think of a solution approach, then try and submit the question on editor tab.
3. We strongly advise you to watch the solution video for prescribed approach.

Example

Input
3
Output
5
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