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 i in range(t):
    n = int(input())
    s = list(map(int, input().split()))
    ma = max(s)
    mai = s.index(ma)
    f = 0
    for i in range(n):
        if ma != s[i]:
            print(mai)
            f = 1
            break
    if f == 0:
        print(-1)

