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)

// https://atcoder.jp/contests/abc159/tasks/abc159_b

#include <iostream>
#include <string>

using namespace std;

bool is_palindrome(string s) {
    const int N = s.size();
    for (int i = 0; i < N / 2; ++i) {
        if (s[i] != s[N - 1 - i]) return false;
    }
    return true;
}

bool solve(string s) {
    const int N = s.size();
    auto s1 = s.substr(0, (N-1)/2);
    auto s2 = s.substr((N+3)/2 - 1);
    return
        is_palindrome(s) &&
        is_palindrome(s1) &&
        is_palindrome(s2);
}

int main() {
    string S;
    cin >> S;
    auto ans = solve(S);
    cout << (ans ? "Yes" : "No") << endl;

    return 0;
}