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;
#define ll long long
const int x = 123;
bool chk(string s)
{
	int l = s.size(), i;
	unsigned long long sd = 101, p = 1, d = 0, h = 0;
	for (i = l - 1; i >= 0; i--)
		{
			d = d + s[i] * p;
			p = p * sd;
			h = h * sd + s[i];
		}
	return (d == h);
}
int main()
{
	ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
	string s;
	cin >> s;
	int sz = s.size();
	ll l1 = sz / 2;
	ll l2 = (sz + 3) / 2;
	if (chk(s) && chk(s.substr(0, l1)) && chk(s.substr(l2 - 1, l1)))
		cout << "Yes" << endl;
	else cout << "No" << endl;
	//main();
}