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()))

	best = max(a)
	answer = -1
	for i in range(n):
		if a[i] != best: continue
		if (i-1 >= 0 and a[i-1] < a[i]) or (i+1 < n and a[i] > a[i+1]):
			answer = i + 1
			break
	
	print(answer)