import java.io.*;
import java.util.*;

public class ReadFile 
{
    public static void main(String[] args) throws Exception 
    {
        TreeSet<Integer> set = new TreeSet<Integer>();
        
        //首先生成20000个随机数到set中
        int num = 0;
        while (true)
        {
            if (set.add((int) (Math.random() * 40000000)))
            {
                num++;
            }
            if (num == 20000)
            {
                break;
            }
        }
        
        //根据set的数据读取响应的行数据
        BufferedReader in = new BufferedReader(new FileReader("in.txt"));
        PrintWriter out = new PrintWriter(new FileWriter("out.txt"));
        for (int i = 0; i < 40000000; i++)
        {
            String str = in.readLine();
            if (set.contains(i))
            {
                out.println(str);
            }
        }
        in.close();
        out.close();
    }
}