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())
  lst=list(map(int,input().split()))
  index=-1
  ans=max(lst)
  for i in range(n):
    if lst[i]==ans and ((i>0 and lst[i-1]<lst[i]) or (i<n-1 and lst[i+1]<lst[i])):
      index=i+1
  print(index)
