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 System.Linq;
using System.Collections.Generic;
using System.Numerics;

namespace abc145
{
    class Program
    {
        static void Main(string[] args)
        {
            //Console.SetIn(new StreamReader("input.txt"));
            solve_abc145B();
        }

        public static void solve_abc145B()
        {
            int n = Convert.ToInt32(Console.ReadLine());
            string s = Console.ReadLine();

            if (n % 2 != 0)
            {
                Console.WriteLine("No");
            }
            else
            {
                bool ok = true;
                for (int i = 0; i < n / 2; i++)
                {
                    if (s[i] != s[i + n / 2])
                    {
                        ok = false;
                        break;
                    }
                }

                if (ok)
                {
                    Console.WriteLine("Yes");
                }
                else
                {
                    Console.WriteLine("No");
                }
            }
        }

        public static void solve_abc145A()
        {
            int r = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine(r * r);
        }
    }
}