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

for _ in range(int(input())):
	n = int(input())
	a = list(map(int,input().split()))
	m = max(a)
	ind=-1
	for i in range(len(a)):
		if a[i] == m and ((i>0 and a[i] > a[i-1]) or (i < n-1 and a[i] > a[i+1])):
			ind = i + 1
	print(ind)