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 C {
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		int t=scanner.nextInt();
		while(t-->0){
			int n=scanner.nextInt();
			int arr[]=new int[n];
			for(int i=0;i<n;i++){
				arr[i]=scanner.nextInt();
			}
			int min=arr[0],max=arr[0],index=-1;
			for(int i=0;i<n;i++){
				min=Math.min(min, arr[i]);
				max=Math.max(max, arr[i]);
			}
//			System.out.println(min+" "+max);
			if(min==max){
				System.out.println(-1);
				continue;
			}
			for(int i=1;i<n;i++){
				if(arr[i]==max&&arr[i-1]<max){
					index=i;
					break;
				}
			}
//			System.out.println(index);
			if(index==-1)
			for(int i=0;i<n-1;i++){
				if(arr[i]==max&&arr[i+1]<max){
					index=i;
					break;
				}
			}
			System.out.println(index+1);
		}
	}
}
