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 i in range(t):
	n = int(input())
	a = list(map(int, input().split()))
	ans = -1
	mx = max(a)
	for j in range(n):
		if a[j] == mx and ((j > 0 and a[j] > a[j - 1]) or (j < n - 1 and a[j] > a[j + 1])):
			ans = j + 1
			break
	print(ans)
