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).

Your Task:
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 ≤ 10^{9}

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