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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
  $s = str_split(trim(fgets(STDIN)));
  $n=count($s);

  for($i=0;$i<($n-1)/2;$i++){
    if($s[$i]!=$s[$n-1-$i]){
      echo "No";
      exit;
    }
  }
  
  $x = intdiv(($n-1)/2, 2);

  if(($n-1)/2%2==0){
    for($i=0;$i<$x;$i++){
      if($s[$i]!=$s[$x*2-1-$i]){
        echo "No";
        exit;
      }
    }
  }else{
    for($i=0;$i<$x;$i++){
      if($s[$i]!=$s[$x*2-$i]){
        echo "No";
        exit;
      }
    }
  }

  echo "Yes";