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

#define endl '\n'
#define rep(i, a, b) for(int i = (a); i <= (b); i++)
#define per(i, a, b) for(int i = (a); i >= (b); i--)
#define rept(i, a, ne) for(int i = (a); ~i ; i=ne[i])
#define debug(x) cout<<#x<<": "<<x<<endl
#define fi first
#define sec second
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
typedef long long LL;
typedef long double  LD;
typedef unsigned long long ULL;
typedef vector<int> VI;
typedef pair<int,int>PII;
const int N=3e3+10;
int a[N];
int b[N];
PII res[N*N];
int c[N];
int d[N];
void slove()
{
    int n;
    cin>>n;
    rep(i,1,n)
    {
       cin>>a[i];
       c[a[i]]=i; 
    }

    rep(i,1,n)
    {
       cin>>b[i]; 
       d[b[i]]=i;
    }
    
    int num=0;
    per(i,n,1)
    {
        while(1)
        {
            if(c[i]==d[i])break;
            int mai=0;
            rep(j,c[i]+1,d[i])
            {
                if(a[j]==b[j])
                continue;
                if(mai==0)
                mai=j;
                else if(mai<a[j])
                mai=j;
            }
            if(mai==0||a[mai]>=i)
            {
                cout<<-1<<endl;
                return;
            }
            int p=a[mai];
            swap(a[c[i]],a[mai]);
            swap(c[i],c[p]);  
            res[++num]={c[i],c[p]};
        }
        

    }
    rep(i,1,n)
    {
        if(a[i]!=b[i])
        {
            cout<<-1<<endl;
            return;
        }
    }
    cout<<num<<endl;
    rep(i,1,num)
    {
        if(res[i].fi>res[i].sec)
        {
            swap(res[i].fi,res[i].sec);
        }
        cout<<res[i].fi<<' '<<res[i].sec<<endl;
    }
    
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
//	cout << fixed << setprecision(9);
    int t=1;
	cin>>t;
    while(t--)
    {
        slove();
    }


    return 0;
}
//#pragma GCC optimize(2)