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

# -*- coding: utf-8 -*-
"""Untitled8.ipynb

Automatically generated by Colaboratory.

Original file is located at
    https://colab.research.google.com/drive/11pXv2Y6O-vHeswG8-dOfYluYwZ5zZKss
"""

for test in range(int(input())):
  n=int(input())
  arr=list(map(int,input().split()))
  maxi=-float("inf")
  for i in arr:
    maxi=max(i,maxi)
  idx=-1
  for i in range(n):
    if arr[i]!=maxi: 
      continue
    if (i>0 and arr[i-1]!=maxi):
      idx=i+1
    if(i<n-1 and arr[i+1]!=maxi):
      idx=i+1
  print(idx)

