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: Accepted)

#include <bits/stdc++.h>
using namespace std;
 

    //組み合わせの数nCrを計算
    int combi(int n, int r){
        int num = 1;
        for(int i = 1; i <= r; i++){
            num = num * (n - i + 1) / i;
        }
        return num;
    }

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

  int L = S.size()/2;
  for(int i =0;i<L; i++){
    if(S.at(i) != S.at(S.size()-1-i)){
      cout << "No" << endl;
      return 0;
    }
  }

  L = S.size()/4;
  for (int i =0;i<L;i++){
    if(S.at(i) != S.at(S.size()/2-1-i)){
      cout << "No" << endl;
      return 0;
    }
  }

  cout << "Yes" << endl;
}