Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters.
We will write down this string, starting a new line after every w letters. Print the string obtained by concatenating the letters at the beginnings of these lines from top to bottom.

Constraints

1 \leq w \leq |S| \leq 1000

S consists of lowercase English letters.

w is an integer.

Input

Input is given from Standard Input in the following format:

S
w

Output

Print the desired string in one line.

Sample Input 1

abcdefgh
3

Sample Output 1

adg

When we write down abcdefgh, starting a new line after every three letters, we get the following:

abc

def

gh

Concatenating the letters at the beginnings of these lines, we obtain adg.

Sample Input 2

lllll
1

Sample Output 2

lllll

Sample Input 3

souuundhound
2

Sample Output 3

suudon

Solution in JavaScript (node.js v5.12) (judge verdict: Runtime Error)

function Main(input) {
  let s = input[0],
      w = input[1];
  let args = new Array(), ans;
  for(let i = 0; s.length > i + 1; i += w){
    args.push(s.substr(i, w));
  }
  for(let i = 0; i < args.length; i++){
    ans += args[i].slice(0, 1);
  }

  console.log(ans);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));