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())
    a = list(map(int, input().split()))
    t=max(a)
    if t == min(a):
        print(-1)
    else:
        j = a.index(t) + 1
        if j ==1:
            while j <= n - 1 and a[j] == t:
                j += 1
        print(j)
