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 z in range(int(input())):
    n = int(input())
    a = [int(i) for i in input().split()]
    if a.count(a[0]) == n:
        print("-1")
    else:
        print(a.index(max(a))+1)
