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 Common Lisp (SBCL 1.1.14) (judge verdict: Accepted)

(defun main ()
  (let* ((n (read)) 
         (str (read-line)) 
         (half (floor n 2))
         (str-t (subseq str 0 half)))
    (if (equal str-t (subseq str half)) 
        (format t "~a~%" "Yes")
        (format t "~a~%" "No"))))
(main)