Given an array arr[] of size n, find the first repeating element. The element should occur more than once and the index of its first occurrence should be the smallest.
Note:- The position you return should be according to 1-based indexing.
Example 1:
Input:
n = 7
arr[] = {1, 5, 3, 4, 3, 5, 6}
Output: 2
Explanation:
5 is appearing twice and
its first appearence is at index 2
which is less than 3 whose first
occuring index is 3.
Example 2:
Input:
n = 4
arr[] = {1, 2, 3, 4}
Output: -1
Explanation:
All elements appear only once so
answer is -1.
Your Task:
You don't need to read input or print anything. Complete the function firstRepeated() which takes arr and n as input parameters and returns the position of the first repeating element. If there is no such element, return -1.

Expected Time Complexity: O(n)
Expected Auxilliary Space: O(n)

Constraints:
1 <= n <= 10^{6}
0 <= A_{i}<= 10^{6}

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