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 i in range(int(input())):
    n = int(input())
    l = list(map(int, input().split()))
    m = max(l)
    n2 = min(l)
    if m == n2:
        print(-1)
    else:
        j = l.index(m) + 1
        if j == 1:
            while j <= n - 1 and l[j] == m:
                j += 1
        print(j)