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 _ in range(int(input())):
  n = int(input())
  a = list(map(int, input().split()))
  m = max(a)
  ans=False
  new=[i for i in range(n) if a[i]==m]
  for i in a:
    if i!=m:
      p = a.index(i)
      ans=True
      break
  if ans:
    print(min(new, key=lambda x:abs(x-p))+1)
  else:
    print(-1)