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;

namespace ABC159b
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine();

            int n = s.Length;

            string s1 = s.Substring(0, ((n - 1) / 2));
            int n1 = s1.Length;
            for (int i = 0; i < s1.Length/2; i++)
            {
                if (s1[i] != s1[n1 - 1 - i])
                {
                    Console.WriteLine("No");
                    return;
                }
            }

            string s2 = s.Substring(((n + 3) / 2) - 1,(n-1)/2);
            int n2 = s2.Length;
            for (int i = 0; i < s2.Length / 2; i++)
            {
                if (s2[i] != s2[n2 - 1 - i])
                {
                    Console.WriteLine("No");
                    return;
                }
            }

            for (int i = 0; i < s1.Length / 2; i++)
            {
                if (s1[i] != s2[i])
                {
                    Console.WriteLine("No");
                    return;
                }
            }
            Console.WriteLine("Yes");
        }
    }
}