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;
using System.Collections.Generic;
using System.Text;
using System.Linq;

namespace ABC159 {
    public class B {
        static void Main(string[] args) {
            var s = Console.ReadLine();
            bool strongKaibun = IsKaibun(s) &&
                                IsKaibun(s.Substring(0, s.Length / 2)) &&
                                IsKaibun(s.Substring(s.Length / 2 + 1));
            Console.WriteLine(strongKaibun? "Yes" : "No");
        }

        static bool IsKaibun(string source) {
            int centerIndex = source.Length / 2;
            int offset = source.Length % 2 == 1 ? 0 : 1;
            for (int i = 1; i <= centerIndex; i++) {
                if (source[centerIndex - i] != source[centerIndex + i - offset]) return false;
            }
            return true;
        }
    }
}