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;

namespace AtCoder_solve
{
    class Program
    {
        public const ulong mod = 1000000007;

        static void Main(string[] args)
        {
            long n = long.Parse(Console.ReadLine());
            var s = Console.ReadLine();
            var ans = "";

            if (n % 2 == 1)
            {
                ans = "No";
            }
            else
            {
                for(int i = 0; i < s.Length / 2; i++)
                {
                    ans = "Yes";
                    if (s[i] != s[i + s.Length / 2])
                    {
                        ans = "No";
                        break;
                    }
                }
            }

            Console.WriteLine(ans);
        }
    }
}