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.io.*;
import java.util.*;

public class Rough{
    
    static PrintWriter ww = new PrintWriter(System.out);
    static boolean check(char arr[]){
        for(int i = 1 ; i < arr.length ; i++){
            if(arr[i] != arr[i - 1])return false;
        }
        return true;
    }
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int tt = sc.nextInt();
        while(tt -- > 0){
            int n = sc.nextInt();
            int arr[] = new int[n];
            int max = Integer.MIN_VALUE , count = 0;
            for(int i = 0 ; i < n ; i ++){
                arr[i] = sc.nextInt();
                if(arr[i] > max){
                    max = arr[i];
                    count = 1;
                }
                else if(arr[i] == max)count++;
            }
            if(count == n)ww.println(-1);
            else{
                for(int i = 0 ; i < n ; i ++){
                    if(arr[i] == max){
                        if(i > 0 && arr[i - 1] < max){
                            ww.println(i + 1);
                            break;
                        }
                        if(i < n - 1 && arr[i + 1] < max){
                            ww.println(i + 1);
                            break;
                        }
                    }
                }
            }
        }
        ww.close();
    }
}



