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 scanner = new Scanner(System.in);
        int t = scanner.nextInt();
        while (t-- > 0) {
            int n = scanner.nextInt();
            int[] a = new int[n];
            int largest = -1;
            for (int i=0; i<n; i++) {
                a[i] = scanner.nextInt();
                if (a[i] > largest) {
                    largest = a[i];
                }
            }
            boolean flag = false;
            for (int i=0; i<n; i++) {
                if (a[i] != largest) {
                    flag = true;
                    break;
                }
            }
            if (!flag) {
                System.out.println(-1);
                continue;
            }
            int ans = -1;
            for (int i=0; i<n; i++) {
                if (a[i] == largest) {
                    if (i>0 && a[i-1]<largest) {
                        ans = i+1;
                    } else if (i<n-1 && a[i+1] < largest) {
                        ans = i+1;
                    }
                }
            }
            System.out.println(ans);
        }

    }

}
