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;

public class Test{
  public static void Main(){
    
    //文字列の読み込み
    string s = System.Console.ReadLine();
    int n = s.Length;

    //1~(N-1)/2文字目の回文判定
    bool strong = true;
    for(int i=0; i < (n-1)/2; ++i){
      if(s[i] != s[n-1-i] || s[i] != s[(n-1)/2-1-i]){
        strong = false;
        break;
      }
    }

    if(strong == true){
     	System.Console.WriteLine("Yes");
    } else {
     	System.Console.WriteLine("No");
    }
  }
}