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: Wrong Answer)

using System;

class Kai
{
    static void Main()
    {
        var input = Console.ReadLine();
        Console.WriteLine(Solution(input));
    }

    static string Solution(string s)
    {
        var l  = (s.Length - 1) / 2;
        var s1 = s.Substring(0, l);
        var s2 = s.Substring(l + 1, l);

        return IsKai(s1) && IsKai(s2) ? "Yes" : "No";
    }

    static bool IsKai(string s)
    {
        for (var i = 0; i < s.Length; i++)
        {
            if (s[i] != s[s.Length - 1 -i])
            {
                return false;
            }
        }

        return true;
    }
}