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>

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

int main (void) {
    char    s[100] = {'\0'};
    size_t  s_len;

    scanf("%s", s);

    s_len = strlen(s);
    if ( is_palindrome(s, s_len) &&
         is_palindrome(s, (s_len-1)/2) &&
         is_palindrome(&s[(s_len+3)/2-1], (s_len-1)/2) )
        printf("Yes\n");
    else
        printf("No\n");

    return EXIT_SUCCESS;
}