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

def solve():
    n = int(input())
    a = list(map(int, input().split()))
    m = max(a)
    z = -1
    for i in range(n):
        if a[i] == m:
            if i - 1 >= 0 and a[i] > a[i - 1]:
                z = i + 1
                break
            if i + 1 < n and a[i] > a[i + 1]:
                z = i + 1
                break

    return z

t = int(input())
i = 0
while i < t:
    print(solve())
    i += 1
