#include<iostream>
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define ll long long
#define pb push_back
#define fast_io ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fr(i,a,b) for(int i=a;i<b;i++)
#define loop(x,n) for(int x=0;x<n;x++)
#define mod 1e7
#define inf (1LL<<60)
#define all(x) (x).begin(),(x).end()
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
void precal(){
}
ll helper(vector<ll>v1,vector<ll>v2,vector<pair<ll,ll>>&output){
 for(int i=0;i<v1.size();i++){
    int cur=i;
    for(int j=i+1;j<v1.size();j++){
        if(v1[j]<v1[cur])cur=j;
    }
    if(cur!=i){
      swap(v1[cur],v1[i]);
      swap(v2[cur],v2[i]);
      output.push_back({i,cur});
    }
  }
  for(int i=1;i<v1.size();i++){
      if(v2[i-1]>v2[i]){
        return -1;
      }
  }
  return  output.size();
}
void solve(){
  ll n;cin>>n;
  vector<ll>v1(n);
  vector<ll>v2(n);
  fr(i,0,n)cin>>v1[i];
  fr(i,0,n)cin>>v2[i];

  vector<pair<ll,ll>>output1;
  vector<pair<ll,ll>>output2;
  ll x=helper(v1,v2,output1);
  ll y=helper(v2,v1,output2);
  
  if(x==-1&&y==-1){
    cout<<-1<<endl;
    return;
  }
  if(x!=-1){
    cout<<x<<endl;
    for(int i=0;i<output1.size();i++){
      cout<<output1[i].first+1<<" "<<output1[i].second+1;
      cout<<endl;
    }
  }
  else{
     cout<<y<<endl;
    for(int i=0;i<output2.size();i++){
      cout<<output2[i].first+1<<" "<<output2[i].second+1;
     cout<<endl;
    }
  }
}
int main()
{
fast_io;
cout<<fixed;
cout<<setprecision(10);
precal();
int t=1;cin>>t;
for(int i=1;i<=t;i++)
{
//cout<<Case #<<i<<: ;
solve();
}
 return 0;
}