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 sc=new Scanner(System.in);
        int t=sc.nextInt();
        while (t-- >0){
            int n,max=0,k=0,p = 0;
            n=sc.nextInt();
            int arr[]=new int[n];
            arr[0]=sc.nextInt();
            max=arr[0];
            k=k+1;
            for (int i=1;i<n;i++){
                arr[i]=sc.nextInt();
                if (max>arr[i]){
                    max=arr[i];
                    p=i;
                }else if ((arr[i]<max)&&(arr[i-1]==max)){
                    p=i-1;
                }else if ((arr[i]==max)&&(arr[i-1]<max)){
                    p=i;
                }else if (arr[i]==max){
                    k++;
                }
            }
            if (k==n){
                System.out.println("-1");
            }else {
                System.out.println(p+1);
            }


        }
    }
}
