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;
class Program
{
	static void Main(string[] args)
	{
      string input = Console.ReadLine();
      char[] c = input.ToCharArray();
      int len = c.Length;
      if(len == 3)
      {
        if(c[0] == c[2]) Console.WriteLine("Yes");
        else Console.WriteLine("No");
        return;
      }
      
      for(int i = 0; i < (double)(len - 1) / 4; i++)
      {
        if(c[i] != c[len - 1 - i] || c[i] != c[(len - 1)/2 - i - 1] || c[i] != c[(len + 3)/2 + i - 1])
        {
          Console.WriteLine("No");
          return;
        }
      }
      Console.WriteLine("Yes");
	}
}