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 OCaml (4.02.3) (judge verdict: Wrong Answer)

open Batteries
let cut st str = String.init (String.length str - st) (fun a -> String.get str (a+st))
let get num str = String.init num (fun a -> String.get str a)
let s = read_line ()
let n = String.length s
let n_1 = get ((n-1)/2) s
let n_2 = cut ((n+3)/2-1) s
let half_n1 = get ((String.length n_1)/2) n_1
let end_n1 = cut ((String.length n_1)/2+1) n_1
let half_n2 = get ((String.length n_2)/2) n_2
let end_n2 = cut ((String.length n_2)/2+1) n_2

let _ = (if half_n1 = end_n1 && half_n2 = end_n2 && n_1 = n_2 then "Yes" else "No") |> print_endline