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

for t in range(int(input())):
  n = int(input())
  entry = input().split(' ')
  for i in range(n):
    entry[i] = int(entry[i])
  m = max(entry)
  indx = -2
  for i in range(n):
    if entry[i] == m:
      if i > 0:
        if entry[i-1] < m:
          indx = i
          break
      if i + 1 < n:
        if entry[i+1] < m:
          indx = i
          break
  print(indx+1)
  
