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

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var s = ReadLine();
        if (s.Length % 2 == 1)
        {
            WriteLine("NO");
            return;
        }
        for (var i = 0; i * 2 < s.Length; ++i)
        {
            if (s[i] != s[i + s.Length / 2])
            {
                WriteLine("NO");
                return;
            }
        }
        WriteLine("YES");
    }
}