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;

/**
 *
 * @author dell
 */
public class DominantPrinha {
    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];
            int max=arr[0];
            int count=0;
            for(int i=0;i<n;i++)
            {
                arr[i]=sc.nextInt();
                if(max<=arr[i])
                {
                    max=arr[i];
                }
              }
            int index=-1;
           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);
        }
    }
    
}
