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

I=lambda: map(int, raw_input().split())
t = input()
for _ in xrange(t):
	n = input()
	a = I()
	M = max(a)
	r = -1
	for i in xrange(n):
		if a[i] == M:
			if i>0 and a[i-1] < M:
				r = i+1
				break
			if i<n-1 and a[i+1] < M:
				r = i+1
				break
	print r	