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: Wrong Answer)

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

int is_palindrome(char *s, int n) {
    int low, high;
    if (!n) n = strlen(s);
    low = 0;
    high = n - 1;
    while (low < high) {
        if (s[low++] != s[high--])
            return 0;
    }
    return 1;
}

int main() {
    char S[100], *tmp;
    int len, index;
    fgets(S, 100, stdin);
    len = strlen(S);
    S[--len] = 0;
    if (len == 3) {
        if (is_palindrome(S, len)) puts("Yes");
        else puts("No");
        return 0;
    }
    if (!is_palindrome(S, len)) {
        puts("No");
        return 0;
    } else if (!is_palindrome(S, len / 2)) {
        puts("No");
        return 0;
    } else if (!is_palindrome(S + len / 2 + 1, 0)) {
        puts("No");
        return 0;
    }

    puts("Yes");
}