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>

bool IsPalindrome(const std::string &str) {
  const size_t half_size = str.size() / 2;
  const size_t size = str.size();
  for (int i = 0; i <= half_size; ++i) {
    if (str.at(i) != str.at(str.size() - (i + 1))) {
      return false;
    }
  }
  return true;
}

int main(int, char **) {
  std::string S;
  std::cin >> S;
  const size_t N = S.size();
  const size_t substr_size = (N - 1) / 2;
  const std::string first{S.substr(0, substr_size)};
  const std::string second{S.substr(((N + 3) / 2) - 1, substr_size)};
  if (IsPalindrome(first) && IsPalindrome(second)) {
    std::cout << "Yes" << std::endl;
  } else {
    std::cout << "No" << std::endl;
  }
  return 0;
}