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 q in range(int(input())):
	n = int(input())
	a = list(map(int, input().split()))
	mx = max(a)
	for i in range(n):
		if a[i] == mx:
			if i + 1 != n and a[i] > a[i + 1]:
				res = i + 1
				break
			if i != 0 and a[i] > a[i - 1]:
				res = i + 1
				break
	print(-1 if len(set(a)) == 1 else res)