using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string[] arr = Console.ReadLine().Split(' ').ToArray();

        for(int i = 0; i < arr.Length;i++)

        {

            int length = arr[i].Length;

            if(length == 4)

            {

                Console.WriteLine(arr[i]);

            }

        }

    }

}