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.LinkedList;
import java.util.Scanner;

public class main
{		
	
	    public static void main(String args[])
	    {
	    	Scanner s=new Scanner(System.in);
	    	int t=s.nextInt();
	    	
	    	while(t-->0) {
	    		int n=s.nextInt();
	    		int[] arr =new int[n];
	    		int max=0;
	    		int index=-1;
	    		
	    		for(int i=0;i<n;i++) {
	    			arr[i]=s.nextInt();
	    			max=Math.max(max, arr[i]);
	    		}
	    		
	    		for(int i=0;i<n;i++) {
	    			if(max==arr[i]) {
	    				
	    				if(i==0) {
	    					if(arr[1]<arr[0]) {
	    						index=0+1;
	    						break;
	    					}	    					
	    				}
	    				
	    				else if(i==(n-1)) {
	    					if(arr[n-2]<arr[n-1]) {
	    						index=n-1+1;
	    						break;
	    					}
	    				}
	    				
	    				else {
	    					if(arr[i+1]<arr[i] || arr[i-1]<arr[i]) {
	    						index=i+1;
	    						break;
	    					}
	    				}
	    				
	    				
	    			}
	    		}
	    		
	    		System.out.println(index);
	    		
   
	    	}
   			
		}	
}