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())
    p =list(map(int, input().split()))
    m = max(p)
    p = [m] + p + [m]
    mi = -1
    for j in range(1, n + 1):
        if (p[j] == m) and ((p[j - 1] < m) or (p[j + 1] < m)):
            mi = j
    print(mi)