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 Java7 (OpenJDK 1.7.0) (judge verdict: Runtime Error)

import java.util.*;
import java.math.*;

public class Main {
    public static void main(String[] args)   {
        
    	Scanner sc1= new Scanner(System.in);
    	int n=sc1.nextInt();
    	
    	Scanner sc2= new Scanner(System.in);
    	String s = sc2.nextLine();
    	String s_half = s.substring(0, n/2);
    	String s_half2 = s.substring(n/2, n);
    	if(s_half.equals(s_half2)) {
    		System.out.println("Yes");
    	}else {
    		System.out.println("No");
    	}
    	
    }
}