Problem:
Score : 200 points

Problem Statement

Given are a positive integer N and a string S of length N consisting of lowercase English letters.

Determine whether the string is a concatenation of two copies of some string.
That is, determine whether there is a string T such that S = T + T.

Constraints

1 \leq N \leq 100

S consists of lowercase English letters.

|S| = N

Input

Input is given from Standard Input in the following format:

N
S

Output

If S is a concatenation of two copies of some string, print Yes; otherwise, print No.

Sample Input 1

6
abcabc

Sample Output 1

Yes

Let T = abc, and S = T + T.

Sample Input 2

6
abcadc

Sample Output 2

No

Sample Input 3

1
z

Sample Output 3

No

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

class Program
{
	static void Main(string[] args)
	{
		int N,n;
		string s,S1 = "",S2 = "";
		N = int.Parse(Console.ReadLine());
		s = Console.ReadLine();
		if(N % 2 == 1)
		{
			Console.Write("No");
		}
		else
		{
			n = (N / 2) - 1;
			for(int i = 0;i <= n;i++)
			{
				S1 = S1 + s[i];
				S2 = S2 + s[i + (n + 1)];
            }
			if (S1 == S2) Console.Write("Yes");
			else Console.Write("No");
		}
		Console.ReadKey();
	}
}