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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <limits.h>

int is_palindrome(char *str, const int n)
{
	for (int i = 0; i < n / 2; i++)
		if (str[i] != str[n - i - 1])
			return 0;
	return 1;
}

int main(void)
{
	char str[100] = {
		0,
	};
	int len;
	scanf("%s", str);
	len = strlen(str);

	if (is_palindrome(str, len))
	{
		if (is_palindrome(str, (len - 1) / 2))
		{
			if (is_palindrome(str + (len + 3) / 2 - 1, (len - 3) / 2) + 1)
			{
				printf("Yes");
				return 0;
			}
		}
	}

	printf("No");
	return 0;
}