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.Numerics;

namespace atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine();

            if (!IsCirculation(s))
            {
                Console.WriteLine("No");
            }
            else if (!IsCirculation(s.Substring(0, (s.Length - 1) / 2)))
            {
                Console.WriteLine("No");
            }
            else if (!IsCirculation(s.Substring((s.Length + 2) / 2)))
            {
                Console.WriteLine("No");
            }
            else
            {
                Console.WriteLine("Yes");
            }
        }

        private static bool IsCirculation(string str)
        {
            var isEven = str.Length % 2 == 0;
            var halfCnt = str.Length / 2;
            if (isEven)
            {
                return str.Substring(0, halfCnt) == new string(str.Substring(halfCnt)
                    .Reverse().ToArray());
            }

            return str.Substring(0, halfCnt) == new string(str.Substring(halfCnt + 1).Reverse().ToArray());
        }
    }
}