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

n = int(input())
for _ in range(n):
	n = int(input())
	l = list(map(int, input().split()))
	i = j = l.index(max(l))
	while j < n and l[i] == l[j]:
		j += 1
	print((i or [-2, j - 1][j < n]) + 1)