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 Hello
{
    public static void Main()
    {
        var s = Console.ReadLine().Trim();
        Console.WriteLine(getAns(s) ? "Yes" : "No");
    }
    static bool getAns(string s)
    {
        var sL = s.Length;
        if (!check(s, 0, sL - 1)) return false;
        if (!check(s, 0, sL / 2 - 1)) return false;
        return check(s, sL / 2 + 1, sL - 1);
    }
    static bool check(string s, int L, int r)
    {
        var imax = (r - L + 1) / 2;
        for (int i = 0; i < imax; i++)
            if (s[L + i] != s[r - i]) return false;
        return true;
    }
}