/*
 *
 ********************************************************************************************
 * AUTHOR : Vijju123                                                                        *
 * Language: C++14                                                                          *
 * Purpose: -                                                                               *
 * IDE used: Codechef IDE.                                                                  *
 ********************************************************************************************
 *
 Comments will be included in practice problems if it helps ^^
 */



#include <iostream>
#include<bits/stdc++.h>
using namespace std;

int main() {
	// your code goes here
	#ifdef JUDGE
    freopen("input.txt", "rt", stdin);
    freopen("output.txt", "wt", stdout);
    #endif
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);
	cout.tie(NULL);
	int t;
	cin>>t;
	while(t--)
	{
	    int n;
	    cin>>n;
	    int a[n],b[n],ans=0;
	    int i,j;
	    //Input 
	    for(i=0;i<n;i++)
	        cin>>a[i];
	    for(i=0;i<n;i++)
	        cin>>b[i];
	    
	    deque<int> q;
	    int possible=1;
	    //Check for case of -1 first.
	    for(i=0;i<n;i++)
	    {
	        if(a[i]<b[i])
	        {
	            possible=0;
	            break;
	        }
	    }
	    if(possible==0)cout<<-1<<endl;
	    else
	    {
	        for(i=0;i<n;i++)
	        {
	            while(!q.empty() and q.back()<b[i])//If there are any recently inserted plants less than b[i]
	                q.pop_back();
	            while(!q.empty() and q.front()>a[i])//If height of any previous b[j] is less than current a[i].
	                q.pop_front();//Please note, that due to our prev. while loop, deque has b[i] in descending
	                //order.
	            if( a[i]!=b[i] and (q.empty() or b[i]!=q.back()) )
	            {
	                ans++;//We cannot find 2 equal b[i] :( . Hence, will need to do 1 more operation.
	                q.push_back(b[i]);
	            }
	        }
	        cout<<ans<<endl;
	    }
	    
	}
	
	return 0;
}