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 Main
{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int t = sc.nextInt();
		int [] array = new int[1000001];
		while(t!=0)
		{
		    int index = -1;
		    int count = 0;
		    int max = 0;
		    int n = sc.nextInt();
		    for(int i=0;i<n;i++)
		    {
		        array[i] = sc.nextInt();
		        if(array[i]>max)
		        {
		            max = array[i];
		            index = i + 1;
		        }
		    }
		   for(int i = 0;i<n;i++){
		       if(max == array[i]){
		           count++;
		       }
		   }
		   //System.out.println(count);
		    if(count > 1)
		    {
		        for(int i = 0;i<n-1;i++)
		        {
		            if((array[i] == max) && (array[i]>array[i + 1])){
		              index = i + 1; 
		              break;
		            }
		            index = -1;
		        }
		        if(index == 1){
		           for(int i =  n-1 ;i>=1;i--)
        		        {
        		            if((array[i] == max) && (array[i]> array[i -1]))
        		            {
        		              index = i + 1; 
        		              break;
        		            }
        		            index = -1;
        		        } 
		        }
		        
		    }
		    System.out.println(index);
		    t--;
		}
	}
}

