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 {

    public static void main(String[] args) {
            Scanner in = new Scanner(System.in);

            int t = in.nextInt();
            for(int f = 0; f < t; ++f) {
                int n = in.nextInt();
                int[] a = new int[n];
                int max = -1;
                for(int i = 0; i < n; ++i) {
                    a[i] = in.nextInt();
                    max = Math.max(max, a[i]);
                }

                int pre = -1, ans = -1;
                for(int i = 0; i < n; ++i) {
                    if(a[i] == max) {
                        if(i - pre > 1)
                            ans = i;
                        pre = i;
                    }
                }

                if(ans == - 1 && pre != n - 1) ans = pre;

                System.out.println(ans == -1 ? ans : ans + 1);

            }
    }
}