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 <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

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

  int n = s.size();

  string s1 = s.substr(0, n / 2);
  string s2 = s.substr(n / 2 + 1, n / 2);

  if (s1 != s2) {
    cout << "No" << endl;
    return 0;
  }

  int m = n / 2;

  string s3 = s1.substr(0, m / 2);
  string s4 = s2.substr(m / 2 + 1, m / 2);
  reverse(s4.begin(), s4.end());
  if (s3 != s4) {
    cout << "No" << endl;
    return 0;
  }

  cout << "Yes" << endl;
  return 0;
}