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.io.*;
import java.util.*;
public class Ishu
{
    static Scanner scan = new Scanner(System.in);
    static void tc()
    {
    int n = scan.nextInt();
    int[] a = new int[n];
    int i,j;
    for(i=0;i<n;++i)
        a[i] = scan.nextInt();
    
    int[] b = a.clone();
    Arrays.sort(a,0,n);
    if(a[0] == a[n-1])
        System.out.println("-1");
    else
        {
        a = b;
        int pos = -1;
        int max = -1;
        for(i=0;i<n;++i)
            if(a[i] > max)
                {
                max = a[i];
                pos = i + 1;
                }
        System.out.println(pos);
        }
    }
    public static void main(String[] args)
    {
    int t = 1;
    t = scan.nextInt();
    while(t-- > 0)
        tc();
    }
}
