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 PHP7 (7.0.15) (judge verdict: Accepted)

<?php
    fscanf(STDIN, "%d", $n);
    fscanf(STDIN, "%s", $s);
    if($n % 2 === 0){
        $cutnum = $n/2;
        $front = substr($s, 0, $cutnum);
        $back = substr($s, $cutnum, $cutnum);
        if($back === $front){
            echo 'Yes';
        }else{
            echo 'No';
        }
    }else{
        echo 'No';
    }
?>