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()))
	val_max = 0
	idx_max = 0
	for i in range(n):
		if i == 0:
			if val_max < a[i] and a[i] > a[i+1]:
				val_max = a[i]
				idx_max = i
		elif i == n - 1:
			if val_max < a[i] and a[i] > a[i-1]:
				val_max = a[i]
				idx_max = i
		else:
			if val_max < a[i] and (a[i] > a[i-1] or a[i] > a[i+1]):
				val_max = a[i]
				idx_max = i
	if val_max == 0:
		print(-1)
	else:
		print(idx_max + 1)

