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

def find(A, x):
	for i in range(len(A)):
		if x == A[i] and i != len(A) - 1 and A[i] > A[i + 1]:
			return i + 1
		elif x == A[i] and i != 0 and A[i] > A[i - 1]:
			return i + 1
	return -1


t = int(input())
for i in range(t):
	n = int(input())
	A = list(map(int, input().split()))
	x = max(A)
	print(find(A, x))