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 item in range(t):
    n = int(input())
    l = list(map(int, input().split()))
    h = max(l)
    li = [item for item in range(n) if l[item] == h and ((item != 0 and l[item-1] < h) or (item != n -1 and l[item+1] < h))]
    print("-1" if len(li) == 0 else li[0]+1)
