code:

#include<bits/stdc++.h>
using namespace std;
const int N=2*1e5+20;
int a[N],b[N];
int n;
void solve(){
    cin>>n;
    for(int i=1;i<=n;i++)scanf("%d",a+i);
    for(int i=1;i<=n;i++)scanf("%d",b+i);
    cout<<2*n<<endl;
    for(int i=1;i<=n*2;i++){
        if(i<=n){
            if(b[i]==1)a[i]=3;
            if(b[i]==2)a[i]=1;
            if(b[i]==3)a[i]=2;
        }
        cout<<a[i]<<' ';
    }
    cout<<endl;
    for(int i=1;i<=n*2;i++){
        if(i>n){
            if(a[i]==1)b[i]=2;
            if(a[i]==2)b[i]=3;
            if(a[i]==3)b[i]=1;
        }
        cout<<b[i]<<' ';
    }
    cout<<endl;
}
int main(){
    int T;
    cin>>T;
    for(int i=1;i<=T;i++){
        solve();
    }
}