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 dorminantPiranha {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Scanner s= new Scanner(System.in);

		int t =s.nextInt();
		while(t-->0) {

			int n =s.nextInt();
			int[] arr = new int[n];

			for(int i=0; i<n; i++) {
				arr[i] = s.nextInt();
			}

			int index=0;

			for(int i=0; i<n; i++) {		
				if(arr[i]>=arr[index] && ((i-1>=0 && arr[i]>arr[i-1]) || (i+1<n && arr[i]>arr[i+1]))  ) {
					index= i;
				}
			}

			int flag=0;

			for(int i=0; i<n; i++) {

				if(arr[i] < arr[index]) {
					flag =1;
				}
			}

			if(flag==1) {
				System.out.println(index+1);
			}
			else {
				System.out.println("-1");
			}
		}
	}
}