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 sol {
	static Scanner scr=new Scanner(System.in);
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int t=scr.nextInt();
		while(t-->0) {
			solve();
		}
	}
	static void solve() {
		int n=scr.nextInt();
		
		int []a=new int[n];
		int max=-1;
		for(int i=0;i<n;i++) {
			a[i]=scr.nextInt();
			max=Math.max(max,a[i]);
		}
		int index=-1;
		for(int i=0;i<n;i++) {
			if(a[i]!=max) {
				continue;
			}
			if(i>0 && a[i-1]!=max) {
				index=i+1;
			}
			if(i<n-1 && a[i+1]!=max ) {
				index=i+1;
			}
		}
		System.out.println(index);
		
	}
}