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: Wrong Answer)

using System;

class Program
{
    static void Main(string[] args)
    {
        string str = Console.ReadLine();
        //string[] str = Console.ReadLine().Split(' ');//2つ以上のスペース区切り入力の取得
        //string str = "<>>><<><<<<<>>><";
        int N = Int32.Parse(str);
        string S = Console.ReadLine();
        //string[] strA = Console.ReadLine().Split(' ');//2つ以上のスペース区切り入力の取得
        //string[] strB = Console.ReadLine().Split(' ');//2つ以上のスペース区切り入力の取得

        //long[] A = new long[N];
        //long[] B = new long[N];

        if( N % 2 != 0 )
        {
            Console.WriteLine("No");
            return;
        }

        int half = N / 2;
        for(int i = 0; i < half; i++ )
        {
            if( S[i] != S[half + i])
            {
                Console.WriteLine("No");
            }
        }

        Console.WriteLine("Yes");
    }
}