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())
 l=[int(num) for num in input().split()]
 m=l.index(max(l))
 j,c=0,0
 M=max(l)
 if(m>0):
  print(m+1)
 else:
  if(l[0]==l[1]):
   for j in range(2,n):
    if(l[j]<l[0]):
     print(j)
     c=1
     break
   if(c==0):
    print(-1)
  else:
   print(1)
     
   