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 j in range(t):
	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)
