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 _ in range(t):
    n = int(input())
    l = list(map(int, input().split()))
    s = set(l)
    if len(s) == 1:
        print(-1)
    else:
        x = max(l)
        index = -1
        for i in range(1, n - 1):
            if l[i] == x and (l[i] > l[i - 1] or l[i] > l[i + 1]):
                index = i + 1
        if l[0] == x and l[0] > l[1]:
            index = 1
        if l[-1] == x and l[-1] > l[-2]:
            index = n
        print(index)