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 _ in range(t):
	n = int(input())
	a = list(map(int, input().split(" ")))
	mx = 0
	for x in a:
		if(x>mx): mx = x
	possible = False
	for x in a:
		if(x!=mx): possible = True
	if(not possible):
		print("-1")
	else:
		for i in range(n):
			if(a[i]==mx and ((i<n-1 and a[i+1]!=mx) or (i>0 and a[i-1]!=mx))):
				print(i+1)
				break