Problem:
Score : 200 points

Problem Statement

A string S of an odd length is said to be a strong palindrome if and only if all of the following conditions are satisfied:

S is a palindrome.

Let N be the length of S. The string formed by the 1-st through ((N-1)/2)-th characters of S is a palindrome.

The string consisting of the (N+3)/2-st through N-th characters of S is a palindrome.

Determine whether S is a strong palindrome.

Constraints

S consists of lowercase English letters.

The length of S is an odd number between 3 and 99 (inclusive).

Input

Input is given from Standard Input in the following format:

S

Output

If S is a strong palindrome, print Yes;
otherwise, print No.

Sample Input 1

akasaka

Sample Output 1

Yes

S is akasaka.

The string formed by the 1-st through the 3-rd characters is aka.

The string formed by the 5-th through the 7-th characters is aka.
All of these are palindromes, so S is a strong palindrome.

Sample Input 2

level

Sample Output 2

No

Sample Input 3

atcoder

Sample Output 3

No

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Windows;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Atcoder
{
    public class Program
    {
        static void Main(string[] args)
        {
            var S = Console.ReadLine();
            var sl = new List<string>();
            for (int i = 0; i < S.Length; i++)
            {
                sl.Add(S[i].ToString());
            }
            var s2 = new string[sl.Count];
            Array.Copy(sl.ToArray(), s2, sl.Count);
            s2 = s2.Reverse().ToArray();
            for (int i = 0; i < sl.Count; i++)
            {
                var aa = sl[i];
                var aa2 = s2[i];
                if (aa != aa2)
                {
                    Console.WriteLine("No");
                    return;
                }
            }
            var N = sl.Count;
            var a = sl.GetRange(0, ((N - 1)/ 2));
            var a2 = new string[a.Count];
            Array.Copy(a.ToArray(), a2, a.Count);
            a2 = a2.Reverse().ToArray();
            for (int i = 0; i < a.Count; i++)
            {
                var aa = a[i];
                var aa2 = a2[i];
                if (aa != aa2)
                {
                    Console.WriteLine("No");
                    return;
                }
            }
            var b = sl.GetRange(((N + 3) / 2) - 1, N - (((N + 3) / 2) - 1));
            var b2 = new string[b.Count];
            Array.Copy(b.ToArray(), b2, b.Count);
            b2 = b2.Reverse().ToArray();
            for (int i = 0; i < a.Count; i++)
            {
                var aa = b[i];
                var aa2 = b2[i];
                if (aa != aa2)
                {
                    Console.WriteLine("No");
                    return;
                }
            }
            Console.WriteLine("Yes");
            Console.ReadLine();
        }
    }
}

public static class Extentions
{
    public static int ToInt(this object obj)
    {
        return int.Parse(obj.ToString());
    }

    public static decimal ToDecimal(this object obj)
    {
        return decimal.Parse(obj.ToString());
    }

    public static double ToDouble(this object obj)
    {
        return double.Parse(obj.ToString());
    }
}