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 Solution {
	
	
    public static void main(String args[] ) throws Exception {
    	
     Scanner sc=new Scanner(System.in);
     int t=sc.nextInt();
     for(int ii=0;ii<t;ii++) {
    	 int n=sc.nextInt();
    	 int arr[]=new int[n];
    	 for(int i=0;i<n;i++) {
    		 arr[i]=sc.nextInt();
    	 }
    	 int max=Integer.MIN_VALUE;
    	 int index=-1;
    	 for(int i=0;i<n;i++) {
    		 if(i==0 &&arr[i]>max&&arr[i+1]<arr[i]) {
    			 max=arr[i];
    			 index=i; 
    		 }
    		 if(i==n-1 &&arr[i]>max&&arr[i-1]<arr[i]) {
    			 max=arr[i];
    			 index=i; 
    		 }
    		 if(i>0&&i<n-1&&(max<arr[i]&&arr[i-1]<arr[i]||max<arr[i]&&arr[i+1]<arr[i]) ) {
    			 max=arr[i];
    			 index=i;
    		 }
    		 
    	 }
    	if(index==-1) {
    		index--;
    	}
    	 System.out.println(index+1);
    	
    	 
    	
    	
 
    }
    }
    
}