Given a number N, find the N^th term in the series 1, 3, 6, 10, 15, 21…

Example 1:

Input :
N = 4 
Output:
10
Explanation:
The 4^th term of the Series is 10.

Example 2:

Input :
N = 3 
Output:
6
Explanation:
The 3^rd term of the Series is 6.

Your Task:
You don't need to read input or print anything. Your task is to complete the function findNthTerm() which takes an Integer N as input and returns the answer.

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

Constraints:
1 <= N <= 10⁴