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 DominantPiranha {

	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 index = -1;
			
			int max = Integer.MIN_VALUE;
			
			for(int val : arr) {
				max = Math.max(max, val);
			}
			
			for(int i=0; i<n; i++) {
				if(arr[i] != max)	continue;
				if(i > 0 && arr[i-1] != max)	index = i + 1;
				if(i < n-1 && arr[i+1] != max)	index = i + 1;
			}
			
			System.out.println(index);
		}
		
		sc.close();
	}

}
