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()))
    r = max(a)
    f = True
    if a[0] == r and a[1] < r:
        print(1)
        continue
    elif a[-1] == r and a[-2] < r:
        print(n)
        continue
    for i in range(1, n - 1):
        if a[i] == r and (a[i - 1] < r or a[i + 1] < r):
            print(i + 1)
            f = False
            break
    if f:
        print(-1)
