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;

namespace ConsoleApp1
{
    class Program
    {
        public static void Main()
        {
            string S = Console.ReadLine();
            int N = S.Length;
            string[] s = new string[N];
            string ans = "Yes";

            for (int i = 0; i < N; i++) 
            {
                s[i] = S.Substring(i, 1);
            }
            for(int i = 0; i < N/2; i++)
            {
                if(s[i] != s[N - 1 - i])
                {
                    ans = "No";
                    i = 100;
                }
            }
            if(ans == "Yes")
            {
                for(int i = 0; i < N/4; i++)
                {
                    if(s[i] != s[(N-1)/2 - 1])
                    {
                        ans = "No";
                        i = 100;
                    }
                }
            }

            Console.WriteLine(ans);
        }
    }
}