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.IO;
using static System.Console;
using static System.Math;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


namespace atcoder
{
    class Program
    {
        //メイン関数
        static void Main(string[] args)
        {
            int n = int.Parse(ReadLine());
            string s = ReadLine();


            if (s.Length % 2 == 0)
                if (s.Substring(0, s.Length / 2) == s.Substring(s.Length / 2, s.Length / 2)) WriteLine("Yes");
                else WriteLine("No");
            else WriteLine("No");
        }




        #region 細々としたツール(関数)

        #region 標準入力
        //変数の入力
        static string scan() => ReadLine();
        static int scanInt() => int.Parse(ReadLine());
        static long scanLong() => long.Parse(ReadLine());

        //配列の入力
        static string[] MultiScan(char Split)
        {
            string[] N = ReadLine().Split(Split);
            return N;
        }
        static string[] MultiScan()
        {
            string[] N = ReadLine().Split(' ');
            return N;
        }

        static List<int> MultiScanInt(char Split)
        {
            string[] N = ReadLine().Split(Split);
            List<int> output = new List<int>();

            for (int i = 0; i < N.Length; i++)
            {
                output.Add(int.Parse(N[i]));
            }

            return output;
        }
        static List<int> MultiScanInt(char Split, int roop)
        { 
            string[] N = ReadLine().Split(Split);
            List<int> output = new List<int>();

            for (int i = 0; i < roop; i++)
            {
                output.Add(int.Parse(N[i]));
            }

            return output;
        }
        #endregion

        #region 数学関連
        public static int Gcd(int a, int b)
        {
            if (a < b)
                // 引数を入替えて自分を呼び出す
                return Gcd(b, a);
            while (b != 0)
            {
                var remainder = a % b;
                a = b;
                b = remainder;
            }
            return a;
        }//最大公約数
        public static int Lcm(int a, int b)
        {
            return a * b / Gcd(a, b);
        }//最小公倍数
        public static int PlusOneSigma(int x, int loop)
        {
            int output = 0;
            for (int i = 0; i < loop; i++)
            {
                output = output + x + i;
            }
            return output;
        }//１づつ加算のシグマ
        #endregion

        #endregion
    }
}