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 Main {
    private static final Scanner scanner = new Scanner(System.in);
    private static final int OO = (int) 1e9 + 10;
    private static final double PI = (double) 22 / 7;
    private static final int[] dx = {0, 1, 0, -1};
    private static final int[] dy = {1, 0, -1, 0};

    public static void main(String[] args) {
        int t = scanner.nextInt();
        while (t-- > 0) {
            int n = scanner.nextInt(), max = -1, ri = -1;
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = scanner.nextInt();
                max = Math.max(max, arr[i]);
            }
            for (int i = 0; i < n; i++) {
                if (arr[i] == max) {
                    if ((i + 1 < n && arr[i + 1] < max) || (i - 1 >= 0 && arr[i - 1] < max)) {
                        ri = i + 1;
                        break;
                    }
                }
            }
            System.out.println(ri);
        }
    }
}