HW2

import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String s = sc.nextLine();

    String s1 = UserMainCode.getMiddleChars(s);
    System.out.println(s1);
  }
}

 class UserMainCode {
    public static String getMiddleChars(String str)
    {
                StringBuffer sb=new StringBuffer();
                 if(str.length()%2==0)
                 {
                 sb.append(str.substring((str.length()/2)-1,(str.length()/2)+1));
                 }
                 return sb.toString();
                 }

    }