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())
while t!=0:
	t-=1
	n=int(input())
	l=list(map(int,input().split()))
	mx=max(l)

	done=0
	for i in range(n):
		if(l[i]==mx):
			if(i-1>=0):
				if(l[i-1]<mx):
					print(i+1)
					done=1
					break
			if(i+1<n):
				if(l[i+1]<mx):
					print(i+1)
					done=1
					break
	if done==0:
		print(-1)
