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{
    static Scanner sc = new Scanner(System.in);
    public static void main(String [] args){
	int t = sc.nextInt();
	while(t-- != 0)solve();
    }
    public static void solve(){
	int n = sc.nextInt();
	int [] arr = new int[n];
	int max = Integer.MIN_VALUE;
	for(int i=0;i<n;i++){
		arr[i] = sc.nextInt();
		max = Math.max(arr[i], max);
	}
	boolean mark = true;
	for(int i=0;i<n;i++){
		if(max != arr[i]){
			mark = false;
			break;
		}
	}
	if(mark){
		System.out.println(-1);
		return;
	}
	mark = false;
	for(int i=0;i<n;i++){
		if(arr[i] == max){
			if(i-1>=0 && arr[i-1]<max)mark = true;
			if(i+1<n && arr[i+1]<max)mark = true;
			if(mark){
				System.out.println((i+1));
				return;
			}
		}
	}
    }
}