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())
	l = list(map(int,input().split()))
	k = max(l)
	if len(set(l)) == 1:
		print(-1)
	else:
		print(l.index(k)+1)