using System;

namespace ConsoleApp169
{
    class Program
    {
        static void Main(string[] args)
        {
            string text = Console.ReadLine();
            MiddleCharPrint(text);
        }

        private static void MiddleCharPrint(string text)
        {
            if(text.Length%2==0)
            {
                Console.Write($"{text[text.Length/2-1]}{text[text.Length/2]}");
                Console.WriteLine();
            }
            else
            {
                Console.Write($"{text[text.Length/2]}");
                Console.WriteLine();
            }




                }
            }
        }