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.Scanner;

public class Main {
    
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        int t=in.nextInt();
        while(t-->0)
        {
            int s=in.nextInt();
            int a[]=new int[s];
           for(int i=0;i<s;i++)
           a[i]=in.nextInt();
           int max=a[0];
           int index=0;
           int j=1;
           for(int i=1;i<s;i++)
           {
                if(max<a[i])
                {
                    max=a[i];
                    index=i;
                }
                if(a[0]==a[i])
                j++;
           }
      
    
           if(j==s)
           System.out.println(-1);
           else
           System.out.println(index);

        }
    }
}
