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())):
	k = int(input())
	a = list(map(int,input().split()))

	m = a[0]
	r = 0

	for i in range(1,k):
		if a[i] >= m and (a[i-1] < a[i] or (i<k-1 and a[i+1] < a[i])):
			m = a[i]
			r = i
	if r>0 or a[1]<a[0]:
		print(r+1)
	else:
		print(-1)