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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		// 入力値
		int n = sc.nextInt();
		String s = sc.next();
		// 文字列の長さ
		int len = n%2 == 0 ? n/2 : 0;
		// 2度繰り返せばOK
		boolean ret = false;
		if(len>0) {
			String c1 = s.substring(0,len);
			String c2 = s.substring(len,s.length());
			if (c1.equals(c2)) {
				ret = true;
			}
		}
		System.out.println(ret?"Yes":"No");
		sc.close();
	}
}