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 PHP (5.6.30) (judge verdict: Accepted)

<?php

$str = trim(fgets(STDIN));
$substr1 = substr($str, 0, (strlen($str)-1)/2);
$substr2 = substr($str, (strlen($str)+3)/2-1, (strlen($str)-1)/2);
print (isKaibun($str) && isKaibun($substr1) && isKaibun($substr2)) ? "Yes" : "No";

function isKaibun($str) {
    $char = preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY);
    $count = count($char);
    for ($i=0; $i < floor($count / 2) ; $i++) { 
        if ($char[$i] != $char[$count-1-$i]) return false;
    }
    return true;
}