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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

main :: IO ()
main = interact $ pickOdds2

pickOdds, pickOdds'
  :: [a] -> [a]
pickOdds []       = []
pickOdds [a]      = [a]
pickOdds (a:b:bs) = a : pickOdds bs 

pickOdds' = map snd . filter (odd . fst) . zip [1..]

pickOdds2 = map snd . filter fst . zip (cycle [True, False])