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>
int main(void){
 int N, i, k;
 double a;
 char S[100];
 scanf("%s", S);
 N = 0;
 while(S[N] != 0){
 N++;
 } 
 i = 0; 
 k = 0;
 for(i = 0;i <= (N - 3) / 4;i++){
  if(S[i] == S[(N - 1) / 2 - 1 - i] && S[(N + 3) / 2 - 1 + i] == S[N - 1 - i]){
   k++;
  }else{
   break;
  }
 }
 a = (double)((N - 3.0) / 4.0);
 if(k > a && k <= a + 1){
  printf("Yes");
 }else{
  printf("No");
 }
 return 0;
}