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Handshakes
Medium Accuracy: 24.23% Submissions: 564 Points: 4

We have N persons sitting on a round table. Any person can do a handshake with any other person.

1
2         3
4

Handshake with 2-3 and 1-4 will cause cross.

In how many ways these N people can make handshakes so that no two handshakes cross each other. N would be even.

Example 1:

Input:
N = 2
Output:
1
Explanation:
{1,2} handshake is
possible.


Example 2:

Input:
N = 4
Output:
2
Explanation:
{{1, 2}, {3, 4}} are the
two handshakes possible.
{{1, 3}, {2, 4}} is another
set of handshakes possible.


You don't need to read input or print anything. Your task is to complete the function count() which takes an integer N as input parameters and returns an integer, the total number of handshakes possible so that no two handshakes cross each other.

Expected Time Complexity: O(2N)
Expected Space Complexity: O(1)

Constraints:
1 <= N <= 30