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 = int(input())
for _ in range(t):
    n = int(input())
    ls = list(map(int, input().split()))
    max_value = max(ls)
    min_value = min(ls)
    if max_value == min_value:
        print(-1)
    else :
        print(ls.index(max_value) + 1)