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 Solution {

public static int mod=100000007;

public static long max=0;
	public static void main(String[] args) {
			Scanner sc=new Scanner(System.in);
			
			int t=sc.nextInt();
			
			for(int a=1;a<=t;a++) {
				
				int n=sc.nextInt();
				
				int arr[]=new int[n];
				
				
				for(int i=0;i<n;i++)
					arr[i]=sc.nextInt();
				int max=arr[0];
				int idx=1;
				boolean flag=false;
				for(int i=1;i<n;i++) {
					
					if(arr[i]==arr[i-1] && !flag) 
					{
						idx=i+1;
						continue;
					}
						
					
					flag=true;
					
					if(arr[i]>max) {
						max=arr[i];
						idx=i+1;
					}
					else if(arr[i]==max && arr[i]==arr[i-1] && i<n-1 && arr[i]>arr[i+1]) {
						idx=i+1;
					}
				}
				
				if(flag)
					System.out.println(idx);
				else
					System.out.println(-1);
				
				
			}
			
			
				
				
	
	}
	
	

	
	
	
	
	
	
	
	
	
	
	}
	

	
	
	
	
	
	


		




		
		
	

	
	
	
	
	
	
		
	
	
	
	
		
	
	

		
		

	
	
	
	

			
	
		
	
	
		
	
	
	
	
	


