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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.IO.Pipes;
using System.Linq;
using System.Numerics;
using System.Text.RegularExpressions;
using System.Threading;

namespace Atcoder
{
	class Program
	{
		//string s = Console.ReadLine();
		//int[] intArray = Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray();
		//int H = intArray[0];
		//int W = intArray[1];
		//int N = int.Parse(Console.ReadLine());
		//List<int> A = new List<int>(Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray());
		//Boolean ok = false;

		//Console.WriteLine(ans);
		//Console.WriteLine("Yes");
		//Console.WriteLine("No");
		//Console.ReadKey();
		//Console.WriteLine(cnt);

		//string[] strArray = Console.ReadLine().Split(' ').ToArray();
		//string S = strArray[0];
		//string T = strArray[1];
		static void Main(string[] args)
		{
			int N = int.Parse(Console.ReadLine());
			string S = Console.ReadLine();
			if(N % 2 != 0)
            {
				Console.WriteLine("No");
				return;
			}
			int len = S.Length;
			string L = S.Substring(0, len / 2);
			string R = S.Substring(len / 2);
			if(L == R)
				Console.WriteLine("Yes");
			else
				Console.WriteLine("No");


		}

		/// <summary>
		/// 回文
		/// </summary>
		/// <param name="Target"></param>
		/// <param name="len"></param>
		/// <returns></returns>
		static bool Palindrome(string Target , int len)
        {
			bool yes = true;

			for(int i = 0;i < len; i++)
            {
				if(Target[i] != Target[len - 1 - i])
                {
					yes = false;
					break;
                }
            }
			return yes;
        }

		/// <summary>
		/// アナグラム
		/// </summary>
		/// <param name="word1"></param>
		/// <param name="word2"></param>
		/// <returns></returns>
		static bool IsAnagramOf(string word1, string word2)
		{
			return word1.OrderBy(x => x).SequenceEqual(word2.OrderBy(x => x));
		}
		/// <summary>
		/// 最小公倍数
		/// </summary>
		/// <param name="a"></param>
		/// <param name="b"></param>
		/// <returns></returns>
		public static BigInteger Lcm(BigInteger a, BigInteger b)
		{
			return a * b / Gcd(a, b);
		}

		/// <summary>
		/// 最大公約数
		/// </summary>
		/// <param name="a"></param>
		/// <param name="b"></param>
		/// <returns></returns>
		public static BigInteger Gcd(BigInteger a, BigInteger 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;
		}
	}
}