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.*;

public class CodeShareTest{
  public static void main(String[] args){
    Scanner in = new Scanner(System.in);
    int t = in.nextInt();
    for (; t > 0; t--)
  {
      int n = in.nextInt();
      int[] a = new int[n];
      int max = 0;
      boolean same = true;
      for (int i = 0; i < n; i++)
      {
        a[i] = in.nextInt();
        if (a[i] > max)
        	max = a[i];
        if (i > 0 && a[i] != a[i - 1])
          same = false;
      }
      if (same)
      {
        System.out.println("-1");
      	continue;
      }
      int ind = -1;
      for (int i = 0; i < n; i++)
      {
        if (a[i] == max && i != 0 && a[i] > a[i - 1])
        {
          ind = i;
          break;
        }
        else if (a[i] == max && i != n - 1 && a[i] > a[i + 1])
        {
        	ind = i;
          break;
        }
      }
      System.out.println(ind + 1);
    }
    in.close();
  }
}