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;
using System.Collections.Generic;
using System.Linq;

class Pg
{
  static void Main(string[] args)
  {
    string input = Console.ReadLine();
    int length = input.Length;
    string pref, suf, prefA, prefB, sufA, sufB;
    int cnt = 0;
    
     pref = input.Substring(0,(length-1)/2 );
     suf = input.Substring((length+3)/2 -1, length-(length+3)/2 + 1);
	var a = suf.Reverse();
    suf = string.Join("", suf.Reverse());
    
    length = pref.Length;
     prefA = pref.Substring(0,(length-1)/2);
     sufA = pref.Substring((length+3)/2 -1 , length-(length+3)/2 + 1);
    	var b = sufA.Reverse();
    sufA = string.Join("", sufA.Reverse());
    
     prefB = suf.Substring(0,(length-1)/2 );
     sufB = suf.Substring((length+3)/2 -1, length-(length+3)/2+1);
        	var c = sufB.Reverse();
    sufB = string.Join("", sufB.Reverse());
    
    if(!pref.Equals(suf)){cnt ++;}
    if(!prefA.Equals(sufA)){cnt ++;}
    if(!prefB.Equals(sufB)){cnt ++;}
    
    string ans;
    if(cnt == 0){ans = "Yes";}else{ans = "No";}
    
    Console.WriteLine(ans);
  }
}