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.ArrayList;
import java.util.Scanner;

public class Main {
    public static int bruh(int[] arr) {
        boolean x=false;
        for (int i = 1; i < arr.length; i++) {
            if(arr[i]!=arr[i-1]){
                x=true;
                break;
            }
            
        }
        if(!x){return -1;}
        int index=0;
        for (int i = 0; i < arr.length; i++) {
            if(arr[i]>=arr[index]){
                index=i;
            }
        }
        return index+1;
    }

    public static void main(String[] args) {
        Scanner obj=new Scanner(System.in);
        int test_case=obj.nextInt();
        
        while(test_case>0){
        int size=obj.nextInt();
        int[] list = new int[size];
        for (int i = 0; i < list.length; i++) {
            list[i]=(obj.nextInt());
            }
        
        System.out.println(bruh(list));
        test_case-=1;   
        }
    }
}
