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

t=int(input())
while(t):
  n=int(input())
  a=list(map(int,input().split()))
  m=max(a)
  y=-1
  if a[0]==m and a[1]<m:
    y=1
  for x in range(1,n-1):
    if a[x]==m and a[x+1]<m:
      y=x+1
      break
    if a[x]==m and a[x-1]<m:
      y=x+1
      break
  if a[n-1]==m and a[n-2]<m:
    y=n
  print(y)
  t-=1