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 w in range(int(input())):
    n = int(input())
    a = [int(x) for x in input().split()]
    st = set(a)
    print(-1 if len(st) == 1 else a.index(max(a)))