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 _ in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))
    m = max(a)
    if a.count(m) < n:
        a.insert(0, m)
        a.append(m)
        for t in range(1, n + 1):
            if a[t] == m and (a[t] > a[t - 1] or a[t] > a[t + 1]):
                print(t)
                break
    else:
        print(-1)
