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.*;
import java.lang.*;
import java.io.*;

public class a {

    public static void main(String[] args) throws java.lang.Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int t = Integer.parseInt(br.readLine());
        while (t-- > 0) {
            int n = Integer.parseInt(br.readLine());
            String[] str = br.readLine().split(" ");
            int[] arr = new int[n];
            int maximumValue = Integer.MIN_VALUE;
            for (int i = 0; i < n; i++) {
                arr[i] = Integer.parseInt(str[i]);
                maximumValue = Math.max(arr[i], maximumValue);
            }
            int index = -1;
            for (int i = 0; i < n; i++) {
                if (arr[i] == maximumValue) {
                    if ((i > 0 && arr[i - 1] < maximumValue) || (i < n - 1 && arr[i + 1] < maximumValue)) {
                        index = i + 1;
                        break;
                    }
                }
            }
            System.out.println(index);
        }
    }
}