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 = input()
for elem in range(t):
    n = input()
    arr = list(map(int,raw_input().split(" ")))
    if min(arr) == max(arr):
        print(-1)
        continue
    print(arr.index(max(arr)))