include<bits/stdc++.h>

using namespace std; int m,n; int a[500005],b[500005],c[1000005]; void Q_sort(){

int aa=1,bb=1,k=1;
while(aa<=n&&bb<=n){
	if(a[aa]<b[bb]) c[k++]=a[aa++];
	else c[k++]=b[bb++];
}
while(aa<=n){
	c[k++]=a[aa++];
}
while(bb<=n){
	c[k++]=b[bb++];
}

} int main(){

cin>>m;
for(int i=1;i<=m;i++){
	cin>>n;
	for(int j=1;j<=n;j++) cin>>a[j];
	for(int j=1;j<=n;j++) cin>>b[j];
	Q_sort();
	for(int j=1;j<=n*2;j++) cout<<c[j]<<" ";
	cout<<endl;
} 
return 0;

}