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: Wrong Answer)

<?php
  

//$abc = explode(" ",trim(fgets(STDIN)));
fscanf(STDIN,"%d",$n);
fscanf(STDIN,"%s",$s);

if($n==1 && $n%2!=0){
  echo "No\n";
  exit;
}
for($i=0;$i<(int)$n/2;$i++){
  $front .= $s[$i];
}

for($i=(int)$n/2;$i<$n;$i++){
  $back .= $s[$i];
}

if($front==$back){
  echo "Yes\n";
}else{
    echo "No\n";

}