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# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Xml;

class Program
{
	static void Main(string[] args)
	{
		string s = Console.ReadLine();
		int A = int.Parse(s.Substring(0, 1));
		int B = int.Parse(s.Substring(1, 1));
		int C = int.Parse(s.Substring(2, 1));
		int D = int.Parse(s.Substring(3, 1));
		string op1 = "";
		string op2 = "";
		string op3 = "";
		string ans = "=7";

		for(int i = 0;i < 2; i++)
		{
            int sumAB;
			check(i, B, A, out  sumAB, out op1);
			for (int j = 0; j < 2; j++)
			{
                 int sumABC;
				check(j, C, sumAB, out sumABC, out op2);
				for (int k = 0; k < 2; k++)
				{
                     int sumABCD;
					check(j, D, sumABC, out sumABCD, out op3);
					if(sumABCD == 7)
					{
						Console.WriteLine(A+op1+B+op2+C+op3+D+ans);
					}
				}
			}
		}
	}

	static void check(int flg,int num ,int oldsum ,out int newsum,out string op)
	{
		if(flg == 0)
		{
			newsum = oldsum + num;
			op = "+";
		}
		else
		{
			newsum = oldsum - num;
			op = "-";
		}
	}
}