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) {
        Scanner sc = new Scanner(System.in);
        
        int t = sc.nextInt();
        
        while(t-- >0){
            int n = sc.nextInt();
            
            int a[] = new int[n];
            
            int max = Integer.MIN_VALUE;
            int max_i = 0;
            
            for(int i=0;i<n;i++){
                a[i] = sc.nextInt();
                if(a[i] > max){
                    max = a[i];
                    max_i = i;
                }
            }
            
            for(int i=0;i<n;i++){
                if(a[i] == max){
                    max_i = i;
                    break;
                }
            }
            int ans = 0;
            Arrays.sort(a);
            boolean flag = true;
            
            if(a[0] == a[a.length-1]){
                System.out.println(-1);
                flag = false;
            }
            else{
                ans = max_i;
            }
            
            if(flag){
              System.out.println(ans + 1);  
            }
            
            
        }
    }
}