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()))
    maxx = -1
    ind = -2
    for i in range(n):
        if a[i] >= maxx and ((i != 0 and a[i] > a[i - 1]) or (i != n - 1 and a[i] > a[i + 1])):
            ind = i
            maxx = a[i]
    print(ind + 1)
