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())
	arr = list(map(int, input().split()))
	m = max(arr)
	val = -1
	for i in range(arr.index(m), n):
		if i - 1 >= 0:
			if arr[i - 1] < m and arr[i] == m:
				val = i + 1
				break
		if i + 1 < n:
			if arr[i + 1] < m and  arr[i] == m:
				val = i + 1
				break
	print(val)
		