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())
while T > 0:
	n = int(input())
	arr = list(map(int, input().split()))
	temp = arr.copy()
	temp.sort()
	if temp[0] == temp[n-1]:
		print(-1)
	else:
		res = -1
		target = temp[n-1]
		for i in range(n):
			if arr[i] == target:
				if (i > 0 and arr[i-1] < target) or (i+1 < n and arr[i+1] < target):
					res = i+1
					break
		print(res)
	T -= 1