Problem:
Score : 200 points

Problem Statement

Given are strings s and t of length N each, both consisting of lowercase English letters.

Let us form a new string by alternating the characters of S and the characters of T, as follows: the first character of S, the first character of T, the second character of S, the second character of T, ..., the N-th character of S, the N-th character of T. Print this new string.

Constraints

1 \leq N \leq 100

|S| = |T| = N

S and T are strings consisting of lowercase English letters.

Input

Input is given from Standard Input in the following format:

N
S T

Output

Print the string formed.

Sample Input 1

2
ip cc

Sample Output 1

icpc

Sample Input 2

8
hmhmnknk uuuuuuuu

Sample Output 2

humuhumunukunuku

Sample Input 3

5
aaaaa aaaaa

Sample Output 3

aaaaaaaaaa

Solution in Common Lisp (SBCL 1.1.14) (judge verdict: Runtime Error)

(defun gen (str1 str2 &optional s)
  (cond ((equal str1 "") s)
    (t (gen (subseq str1 1) (subseq str2 1)
       (concatenate 'string s (subseq str1 0 1)(subseq str2 0 1)))))
  )


(let* ((n (read))
       (s (read-line))
       (str1 (subseq s 0 n))
       (str2 (subseq s (+ n 1))))
      (format t "~A~%" (gen str1 str2)))a