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.*;
import java.math.*;
public class C {

	public static void main(String[] args) 
	{
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in);
		int t,n,i,j=0,k,p=0,fg=0,m,ans=0,max=-1;
		t=sc.nextInt();
		while(t-->0)
		{
			n=sc.nextInt();
			int arr[]=new int[n];
			for(i=0;i<n;i++)
				arr[i]=sc.nextInt();
			for(i=1;i<n;i++)
				if(arr[0]-arr[i]!=0)
					break;
			if(i==n)
			{
				System.out.println("-1");
				continue;
			}
			for(i=0;i<n;i++)
				if(max!=Math.max(max, arr[i]))
				{
					max=Math.max(max, arr[i]);
					j=i+1;
				}
			System.out.println(j);
			ans=0;
			max=-1;
		}
	}
}