import java.io.*;
import java.util.*;
 
class Solution
{
	public static void main(String args[]) throws Exception
	{
		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int T = Integer.parseInt(br.readLine());
		for(int case_t=1;case_t<=T;case_t++)
		{
			int N = Integer.parseInt(br.readLine());
			String[] F = new String[N];
			for(int i=1;i<N;i++)
			{
				F[i] = br.readLine();
			}
			for(int i=1;i<N;i++)
			{
				bw.write(F[i].charAt(3));
			}
		}
		bw.flush();
		bw.close();
		br.close();
	}
 
}