using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;

namespace YukiCoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            new Program().Solve();
        }

        public void Solve()
        {
            string s = ReadLine();

            if (s.Length % 2 == 0 && (s.Substring(0,s.Length/2) == s.Substring(s.Length/2 , s.Length /2)))
            {
               WriteLine("YES"); 
            }
            else
            {
                WriteLine("NO");
            }
        }
    }
}