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;

namespace tst
{
    class Program
    {
        public static bool Palindrome(string s, int n)
        {
            int mid = (n + 1) / 2;
            for(int i=0; i<mid; i++)
            {
                if (s[i] != s[n - i - 1]) return false;
            }
            return true;

        }
        public static void Main()
        {
            string s = Console.ReadLine();
            int n = s.Length;
            bool flag=false;
            if (Palindrome(s,n))
            {
                int l = (n - 1) / 2;
                string s1 = s.Substring(0, (n - 1) / 2);
                string s2 = s.Substring(((n + 3) / 2)-1);
                if (Palindrome(s1, l) && Palindrome(s2, l))
                {
                    flag = true;
                }
            }
            if (flag) Console.WriteLine("Yes");
            else Console.WriteLine("No");
        }
    }
}