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 i in range(t):
    n = int(input())
    a = [int(item) for item in input().split()]
    k = a.index(max(a))
    if k == len(a)-1:
        print(k+1)
    else:
        for i in range(k, n-1):
            if a[i] > a[i+1] or a[i] > a[i-1]:
                print(i)
                break
        else:
            print(-1)
