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()))
	aux = [0 for i in range(n)]
	for i in range(n):
		if i>0 and arr[i] > arr[i-1]:
			aux[i] = 1
		if i<n-1 and arr[i] > arr[i+1]:
			aux[i] = 1
	m = max(arr)
	ans = -1
	for i in range(n):
		if arr[i] == m and aux[i] == 1:
			ans = i+1
			break
	print(ans)