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{
    static int dominant(int []arr,int n){
        int count = 0;
        for(int i=0;i<n-1;i++)
        {
            if(arr[i] == arr[i+1])
                count++;
        }
        if(count == n-1)
            return -1;
        int max = Integer.MIN_VALUE;
        int maind = 0;
        for(int i=0;i<n;i++)
        {
            if(max<arr[i] && ((i+1<n &&arr[i]>arr[i+1]) || (i-1>=0 && arr[i]>arr[i-1]))){
                max = arr[i];
                maind = i+1;
            }
        }
        return maind;
    }
    public static void main (String[] args) {
        Scanner scan = new Scanner(System.in);
        int t = scan.nextInt();
        for(int j=1;j<t+1;j++)
        {
            int n = scan.nextInt();
            int []arr = new int [n];
            for(int i=0;i<n;i++)
                arr[i] = scan.nextInt();
            System.out.println(dominant(arr,n));
        }
    }
}