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 C1433 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int t = input.nextInt();
        int[] arr;
        while(t--!=0){
            int n = input.nextInt();
            arr = new int[n];
            for(int i=0;i<n;i++){
                arr[i] = input.nextInt();
            }
            int i;
            for(i=1;i<n-1;i++){
                if(arr[i - 1] < arr[i]){
                    break;
                }else if(arr[i + 1] < arr[i]){
                    break;
                }
            }
            if(i == arr.length - 1)
                if(arr[i] > arr[i - 1])
                    System.out.println(i+1);
                else
                    System.out.println(-1);
            else
                System.out.println(i+1);
        }
        input.close();
    }
}
