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.lang.*;
import java.io.*;
public class main{ 
	 public static void main(String args[])
	    { 
		 	Scanner sc = new Scanner(System.in);
		 	int t = sc.nextInt();
		 	while(t-->0)
		 	{
		 		int n = sc.nextInt();
		 		int a[] = new int[n],ans=-1,mx=0;
		 		boolean flag=true;
		 		for(int i=0;i<n;i++)
		 		{
		 			a[i]=sc.nextInt();
		 		}
		 		for(int i=0;i<n;i++)
		 		{
		 			mx = Math.max(mx,a[i]);
		 		}
		 		for (int i = 0; i < n; ++i) 
		 		{
		 			if (a[i] != mx) continue;
		 			if (i > 0 && a[i - 1] != mx) ans = i + 1;
		 			if (i < n - 1 && a[i + 1] != mx) ans = i + 1;
		 		}
		 		System.out.println(ans);
		 	}
	    }
}