import java.util.Scanner;
public class largestNumArray {
static Scanner s = new Scanner(System.in);
static int t;
public static void main(String[] args) {
// TODO Auto-generated method stub
t = s.nextInt();
String[][] arr = new String[t][];
for(int i=0; i<t; i++) {
arr[i] = takeInput();
findTheLargest(arr[i]);
}
printArray(arr);
}
private static void printArray(String[][] arr) {
// TODO Auto-generated method stub
for(int i=0; i<t; i++) {
for(int j=0; j<arr[i].length; j++) {
System.out.print(arr[i][j]);
}
System.out.println();
}
}
private static void findTheLargest(String[] arr) {
// TODO Auto-generated method stub
for(int i=0; i<arr.length; i++) {
for(int j=i+1; j<arr.length; j++) {
String ij = arr[i] + arr[j];
String ji = arr[j] + arr[i];
if(checkParams(ij, ji)) {
swap(arr, i , j);
}
}
}
}
private static void swap(String[] arr, int i, int j) {
// TODO Auto-generated method stub
String temp = arr[i];
arr[i]= arr[j];
arr[j] = temp;
}
private static boolean checkParams(String ij, String ji) {
// TODO Auto-generated method stub
int ab = Integer.parseInt(ij);
int ba = Integer.parseInt(ji);
if(ba > ab) {
return true;
}
return false;
}
private static String[] takeInput() {
// TODO Auto-generated method stub
int n = s.nextInt();
String[] str = new String[n];
for(int i=0; i<n; i++) {
str[i] = s.next();
}
return str;
}
}