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) throws java.lang.Exception
    {
        Scanner s= new Scanner(System.in);
        int t=s.nextInt();
        while(t-- > 0)
        {
            int n=s.nextInt();
            Integer A[]=new Integer[n];
            int max=0;
            for(int i=0; i<n; i++)
            {
                A[i]=s.nextInt();
                max=Math.max(max,A[i]);
            }
            int ans=-1;
            for(int i=0; i<n; i++)
            {
                if(A[i]==max)
                {
                    if(i>0 && A[i-1]<max)
                    {
                        ans=i+1;
                        break;
                    }
                    if(i<n-1 && A[i+1]<max)
                    {
                        ans=i+1;
                        break;
                    }
                }
            }
            System.out.println(ans);
        }
    }
}
