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()))
	mx=0
	for  i in range(n):
		mx=max(mx,a[i])
	index=-1
	for i in range(n):
		if(a[i]==mx):
			flag=True
			if((i-1>=0 and a[i-1]==a[i]) and (i+1<n and a[i+1]==a[i])):
				flag=False
			elif(i==0 and a[i+1]==a[i]):
				flag=False
			elif(i==n-1 and a[i-1]==a[i]):
				flag=False
			if(flag):
				index=i+1
				break
	print(index)


