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())
	arr=list(map(int,input().split()))
	ele=max(arr)
	pos=-1
	for i in range(n):
		if(arr[i]==ele):
			if(i==0):
				if(arr[i+1]<ele):
					pos=i+1
					break
			elif(i==n-1):
				if(arr[i-1]<ele):
					pos=i+1
					break
			else:
				if(arr[i+1]<ele or arr[i-1]<ele):
					pos=i+1
					break
	print(pos)