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 PHP (5.6.30) (judge verdict: Accepted)

<?php

class out {
    public static function println($str = "") {
        echo ($str) . PHP_EOL;
    }
}

while ($line = fgets(STDIN)) {
   $tmp[] = trim($line);
}

$num = intval($tmp[0]);
$half = intval($tmp[0]/2);
$str = $tmp[1];

$word1 =  substr($str, 0, $half);
$word2 = substr($str, $half, $num);

$ans = judge($word1, $word2);

out::println($ans);


function judge($word1, $word2){
    if($word1===$word2){
        return 'Yes';
    }else{
        return 'No';
    }
}

?>