Problem:
Score : 200 points

Problem Statement

You are given a string s consisting of lowercase English letters. Extract all the characters in the odd-indexed positions and print the string obtained by concatenating them. Here, the leftmost character is assigned the index 1.

Constraints

Each character in s is a lowercase English letter.

1≤|s|≤10^5

Input

The input is given from Standard Input in the following format:

s

Output

Print the string obtained by concatenating all the characters in the odd-numbered positions.

Sample Input 1

atcoder

Sample Output 1

acdr

Extract the first character a, the third character c, the fifth character d and the seventh character r to obtain acdr.

Sample Input 2

aaaa

Sample Output 2

aa

Sample Input 3

z

Sample Output 3

z

Sample Input 4

fukuokayamaguchi

Sample Output 4

fkoaaauh

Solution in Common Lisp (SBCL 2.0.3) (judge verdict: Accepted)

(let ((s (concatenate 'list (read-line))))

  (defun solve (lst &optional flag ans)
    (cond
      ((null lst) (concatenate 'string (reverse ans)))
      ((null flag) (solve (cdr lst) t (cons (car lst) ans)))
      (t           (solve (cdr lst) nil ans))))

  (format t "~A~%"
          (solve s)))