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.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder.Abc
{
    class QuestionB
    {
        public static void Main(string[] args)
        {
            var sw = new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);

            // 文字列の入力
            string s = Console.ReadLine();

            if(Kaibun(s)== false) {
                Console.WriteLine("No");

                Console.Out.Flush();
                return;
            }

            var ss = s.Substring(0, (s.Length) / 2);

            if (Kaibun(ss) == false) {
                Console.WriteLine("No");

                Console.Out.Flush();
                return;
            }

            var sss = s.Substring(((s.Length + 2) / 2), s.Length / 2);

            if (Kaibun(sss) == false) {
                Console.WriteLine("No");

                Console.Out.Flush();
                return;
            }

            Console.WriteLine("Yes");

            Console.Out.Flush();
        }

        public static bool Kaibun(string s)
        {
            var n = s.Length;
            var cn = s.Length / 2;

            for(int i = 0; i < cn; i++) {
                if(s[i].Equals(s[n - i- 1]) == false) {
                    return false;
                }
            }

            return true;
        }
    }
}