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 S
{
    public static void main(String args[])
    {
        Scanner scan=new Scanner(System.in);
        int test=scan.nextInt();
        while(test>0)
        {
            test--;
            int n=scan.nextInt();
            int arr[]=new int[n];
            for(int i=0;i<n;i++)
            arr[i]=scan.nextInt();
            int ans=0;
            boolean togo=true;
            //forward march
            for(int i=0;i<n-1;i++)
            {
                if(arr[i]>arr[i+1])
                {
                    //check whether it is greatest amongst all or not
                    int sum=arr[i]+1;
                    boolean b=true;
                    for(int j=0;j<n&&b;j++)
                    {
                        if(arr[j]>=sum)
                        b=false;
                    }
                    if(b)
                    {
                       System.out.println(i+1);
                      togo=false; 
                      break;
                    }
                    
                }
            }
            if(togo)
            {
                
                for(int i=n-1;i>0;i--)
                {
                    if(arr[i]>arr[i-1])
                    {
                      int sum=arr[i]+1;
                    boolean b=true;
                    for(int j=0;j<n&&b;j++)
                    {
                        if(arr[j]>=sum)
                        b=false;
                    }
                    if(b)
                    {
                       System.out.println(i+1);
                      togo=false; 
                      break;
                    }  
                    }
                }
            }
            if(togo)
            System.out.println(-1);
            
            
            
    }
}
}