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 q
    {
    public static void main(String args[])
        {
      Scanner sc=new Scanner(System.in);
     
int t=sc.nextInt();
while(t-->0)
{
       int n=sc.nextInt();
       int a[]=new int[n];
   int c=1;
   a[0]=sc.nextInt();
  int l=0, m=a[0];
     for(int i=1;i<n;i++)
     {
         a[i]=sc.nextInt();
         if(a[i]!=a[i-1])
         l=1;
         if(a[i]>=m && i<n-1)
         {
         m=a[i];
         c=i+1;
     }
     if(i==n-1)
     {
             if(a[i]>m)
             c=i+1;
     }
}
if(l==1)
System.out.println(c);
else
System.out.println("-1");
    }    }    
    }
     