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())
    a = [int(i) for i in input().split()]
    if a.count(max(a)) == len(a):
        print(-1)
    m = max(a)
    for i in range(n):
        if a[i] == m and ((i > 0 and a[i - 1] < a[i]) or (i < n - 1 and a[i + 1] < a[i])):
            print(i + 1)
            break
    
