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 tc in range(t):
	n = int(input())
	a = list(map(int, input().split()))
	mx = max(a)
	ans = [i for i in range(n) if a[i]==mx and ((i!=0 and a[i-1]<mx) or (i!=n-1 and a[i+1]<mx))]
	print("-1" if len(ans)==0 else ans[0]+1)