1
3
5 3 4
 6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

import java.util.Scanner;

public class Round677Div3ProbC {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scn = new Scanner(System.in);
		int t = scn.nextInt();
		while (t > 0) {
			int n = scn.nextInt();
			int[] arr = new int[n];
			int max = Integer.MIN_VALUE;
			for (int i = 0; i < n; ++i) {
				arr[i] = scn.nextInt();
				max = Math.max(max, arr[i]);
			}
			System.out.println(solve(max, arr));
			t--;
		}
	}

	public static int solve(int max, int[] arr) {

		for (int i = 0; i < arr.length; ++i) {

			int x = arr[i];
			if (x == max) {

				if (i != 0) {
					if (arr[i - 1] < x) {
						return i+1;
					}
				}
				if (i != arr.length - 1) {
					if (arr[i + 1] < x) {
						return i+1;
					}
				}

			}

		}
		return -1;

	}

}
