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)
    a = [1e10] + a + [1e10]
    ans = -1
    for i in range(1, n + 1):
        if a[i] > a[i - 1] or a[i] > a[i + 1]:
            if a[i] == m:
                ans = i
    print(ans)
            