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 Scala (2.11.7) (judge verdict: Accepted)


object Main extends App {
  def is_yes(str: String): Boolean = {
    val len = str.length
    return len <= 1 || (str.head == str.last && is_yes(str.slice(1, len - 1)))
  }
  val sc = new java.util.Scanner(System.in)
  val s = sc.next
  val n = s.length

  val no_num = Array(
    s,
    s.slice(0, (n - 1) / 2),
    s.substring((n + 3) / 2 - 1)
  ).filter(!is_yes(_)).length

  println(if (no_num > 0) "No" else "Yes")
}