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 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 = Integer.MIN_VALUE;
            int index = -1;
            HashMap<Integer,Integer> map = new HashMap<>();
            for(int i = 0; i < n; i++){
                arr[i] = s.nextInt();
                if(arr[i] > max){
                    max = arr[i];
                    index = i;
                }   
                map.put(arr[i],map.getOrDefault(arr[i],0) + 1);
            }
            if(map.get(max) == n){
                System.out.println(-1);
            }
            else{
                System.out.println(index);
            }
           
        }

    }
}