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