Given an array of N positive integers, find GCD of all the array elements.

Example 1:

Input: N = 3, arr[] = {2, 4, 6}
Output: 2
Explanation: GCD of 2,4,6 is 2.

Example 2:

Input: N = 1, arr[] = {1}
Output: 1
Explanation: Greatest common divisor of
all the numbers is 1.

Your Task:  
You don't need to read input or print anything. Complete the function gcd()which takes N and array as input parameters and returns the gcd.

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

Constraints:
1 ≤ N, arr[i] ≤ 10⁵