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.*;
 
public class Answer {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int t = sc.nextInt();
		while(t-->0){
			int n = sc.nextInt();
			int[] arr = new int[n];
			for(int i = 0; i<n; i++) arr[i]=sc.nextInt();
			
			int mx = 0;
			for (int it : arr) {
				mx = Math.max(mx, it);
			}
			int idx = -1;
			for (int i = 0; i < n; ++i) {
				if (arr[i] != mx) continue;
				if (i > 0 && arr[i - 1] != mx) idx = i + 1;
				if (i < n - 1 && arr[i + 1] != mx) idx = i + 1;
			}
			System.out.println(idx);
		}
		
	}
}