Maximum Handshakes
Basic Accuracy: 51.13% Submissions: 278 Points: 1

There are N people in a room. If two persons shake hands exactly once, find the maximum number of handshakes possible.

Example 1:

Input: N = 2
Output: 1
Explaination: There are two people and they
can shake hands maximum one time.

Example 2:

Input: N = 3
Output: 3
Explaination: Let the people be person 1, 2 and 3.
So the possible handshakes are (1, 2), (2, 3) and
(1, 3).

You do not need to read input or print anything. Your task is to complete the function handShakes() which takes N as input parameter and returns the maximum number of handshakes possible.

Expected Time Complexity: O(1)
Expected Auxiliary Space: O(1)

Constraints:
2 ≤ N ≤ 109

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