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())


def solve(a, n):
    maxv = max(a)
    for i in range(n):
        if a[i] == maxv:
            if i > 0 and a[i] > a[i-1]:
                return i+1
            if i < n-1 and a[i] > a[i+1]:
                return i+1

    return -1


for _ in range(t):
    n = int(input())
    a = list(map(int, input().split()))

    print(solve(a, n))
