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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>
#include <string>
#include <stack>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    string s;
    cin >> s;

    const int n = (s.length() - 1) / 2;
    string bef = s.substr(0, n);
    string bef_a = bef.substr(0, n/2);
    string bef_b = bef.substr((n+1)/2);
    reverse(bef_b.begin(), bef_b.end());

    string aft = s.substr((s.length() + 1) / 2, n);
    string aft_a = aft.substr(0, n/2);
    string aft_b = aft.substr((n+1)/2);
    reverse(aft_b.begin(), aft_b.end());

    if (bef_a == bef_b && aft_a == aft_b)
    {
        cout << "Yes" << endl;
    }
    else
    {
        cout << "No" << endl;
    }
}