#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
inline int read(){
	char c=getchar();
	int f=1,x=0;
	for(;c<'0'||c>'9';c=getchar()) if(c=='-') f=-1;
	for(;c>='0'&&c<='9';c=getchar()) x=x*10+c-'0';
	return f*x;
}
void solve();
int main(){
	cin.tie(0)->sync_with_stdio(false);
	int t=1;
	cin>>t;
	while(t--)solve();
	return 0;
}

const int N=3000;
int a[N],b[N],ia[N],ib[N],to[N];
void solve(){
	int n;cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		ia[a[i]]=i;
	}
	for(int i=1;i<=n;i++){
		cin>>b[i];
		ib[b[i]]=i;
	}
	for(int i=1;i<=n;i++)to[i]=0;
	
	vector<pair<int,int>>V;
	for(int i=n;i;i--){
		to[ia[i]]=ib[i];
		for(int j=1;j<=to[ia[i]]&&ia[i]>to[ia[i]];j++){
			if(to[j]>to[ia[i]]){
				swap(to[j],to[ia[i]]);
				V.emplace_back(to[j],to[ia[i]]);
				
			}
		}
		if(ia[i]>to[ia[i]]){
			cout<<-1<<endl;
			return;
		}
	}
	
	cout<<V.size()<<endl;
	
	for(auto i=V.rbegin();i!=V.rend();i++){
		cout<<(i->first)<<" "<<(i->second)<<endl;
	}
}