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>
#include<iostream>
#include<string>
using namespace std;
 
int main() {
  
  string str;
  int n,l;
  bool ans = true;
  
  cin>>str;
  n=str.length();
  l=(n-1)/2; //2つの回文の長さ
  
  for(int i=0;i<l;i++)
  {
    ans&=str[i]==str[n-1-i]; 
  }
  for(int i=0;i<(l-1)/2;i++)
  {
    ans &= (str[i] == str[l-1-i]);
    ans &= (str[n-l+1+i] == str[n-1-i]);
  }
  if(ans) cout<<"Yes";
  else cout<<"No";
}