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);
    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 = 0 , count = 0 , in = -1;
            for(int i = 0; i < n ; i ++){
                arr[i] = sc.nextInt();
                if(arr[i] > max){
                    max = arr[i];
                    count  = 1;
                    in = i;
                }
                else if(arr[i] == max){
                    count++;
                }
            }
            if(count == n)ww.println(-1);
            else {
                boolean f = false;
                for(int i = 0 ; i < n - 1 ; i ++){
                    if(arr[i] == max && arr[i + 1] != max){
                        ww.println(i + 1);
                        f= true;
                        break;
                    }
                }
                if(f)continue;
                for(int i = n - 1 ; i > 0  ; i --){
                    if(arr[i] == max && arr[i - 1] != max){
                        ww.println(i + 1);
                        break;
                    }
                }
            }
            
        }
        ww.close();
    }
}



