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 i in range(int(input())):
 n=int(input())
 a=list(map(int,input().split()))
 m=max(a)
 c=0
 for j in range(n):
  if j-1>=0:
   if a[j]==m:
    if a[j]>a[j-1]:
     c=c+1
     break
  if j+1<=n-1:
   if a[j]==m:
    if a[j]>a[j+1]:
     c=c+1
     break
 if c==0:
  print("-1")
 else:
  print(j+1)